the following guide apply to version 2.x, it is recommended to use rather than the 1.6 version because the various geometry nodes controls give much better results, and if you want you can always convert back to particle hairs. in case you have not seen the video walk through on product page, click here.  this guide is consist of several parts: install, bring in hair asset, modify hair asset, finalize hair asset, create hair cards and bake hair textures.

1. Install. 

after you download the addon zip file, open Blender, go to  Edit - Preference - Install the zip file.

the UI_Tab is where you will find the addon panel, you can freely rename it, for example, I have named several addons' tab to "Modeling", so that all of them show up in Modeling side panel, making the blender interface neatly organized. restart blender to take effect.

"Refresh Preview" will refresh image list when new hair asset is added, more on that later.

2. Bring in Hair Assets

by default, you can find addon panel "FHT Geo" on the right side of 3d viewport. click "Import Hair Assets", a window will pop up, where you can choose to import haircut, eyebrow, beard. if nothing is toggle on, none is imported.

one thing to notice is the scale. default blender unit scale is 1 and default cube is 2x2x2 meters.

the default monkey head is 2.7 x 1.7 x 2 meters. whereas average human head is around 0.2 x 0.22 x 0.2 meters. so scale you custom mesh accordingly

haircut, eyebrow, beard are pre-made assets. eyelash is created using "Draw Quick Eyelash". select a mesh to enter draw eyelash modal mode, W or S to rotate, A or D to adjust guide hair density, R to randomize hair distribution, T to toggle upper or lower eyelash. Space Bar or Enter to confirm, Right Mouse Button or Esc to cancel.

3. Modify Hair Assets

Each hair asset is made of a parent mesh and the actual hair curves.

when the parent mesh is select, you can pick the shrinkwrap target, and optionally surface bind to target head mesh, so that the hair asset deforms with the custom head mesh. when you move and scale, do select the parent base mesh and modify it rather than the actual hair curves. otherwise there might be unexpected result due to the parent child relation of the two objects.

select the actual hair curves, go to corresponding panel to start adjust the look. select a preview image and switch the style. 

the difference between switch haircut and hair element is that the switch haircut will replace all current hair curves, the hair element will add selected element

in the Display sub-panel, hair subdivision slider will adjust how smooth the hair looks. when hair display is strip, a Hair Radius slider shows, you can adjust how thick a hair looks. drag Viewport Amount slider to adjust total hair amount shown, low will show only 10% of full hair amount, full to show all.

for the NodeGroup Controls subpanel, it is best for you to play with them to get the hang of it. for the interpolate node group control, press "Edit Mask" will directly bring you to weight paint mode of the parent mesh, where the hair density is controlled by corresponding vertex group. when done, toggle back to object mode and select the hair curves to continue editing. 

the Preset subpanel offers some pre defined hair shape. you can adjust your own shape in the NodeGroup Controls panel and save it as a preset.

for the beard asset, there are bend angle 1 and 2 controls for the beard parent mesh. adjust them to better fit head shape.

the rest of the controls are pretty much the same for all hair assets with the exception of mirror eyebrow and eyelash. for eyebrow, there is a preview mirror eyebrow:

for eyelash, the mirror is at the bottom of the NodeGroup Controls:

Add New Hair is same as blender default Add- Curve - Empty Hair with the addition of the custom geometry nodes setup above

Add Mod simply add custom geometry nodes setup to existing hair curves

4. Finalize Hair.

when you are happy with the look of the hairs. you can transfer the hair to custom mesh. first select the custom head mesh and then the hair curves. go to corresponding hair panel and press transfer hair

for eyebrow assets, when transferring hairs you may want to toggle mirror on.

for eyelash, before transfer hair, make sure it has mirrored part by toggle mirror at the bottom of nodegroup control subpanel.

after the hair transfer. new hair curves are created and they are child object of the custom head mesh. the original hair assets are hidden. at any point if you want to go back and edit hair, you can. simply delete the transferred hair, show the hidden hair asset, modify the look and transfer to custom mesh again.

5. Create Hair Cards

often in game engines, hair cards are used for in game characters. you can turn hair curves into hair cards

the generated hair cards are automatically align to target surface normal. Influence Range will limit the auto surface align. at 0, the hair card does not align, for long hairs, you may limit the auto align to certain point. Embed Root control how deep the starting point of hair cards into the target surface. Rotation will uniformly rotate the hair. Width control the width of the hair cards. Resolution control the mesh resolution. when resolution width is greater than 0.5, bend option shows, it controls the bend of added edge loop in the middle.

for most cases, the hair cards will use double sided material in game. for some case, use Dual Mesh to avoid double sided material. in this case, when dual mesh is on, another layer of the same mesh is created with inverted normal.  another useful case for dual mesh is to create bigger hair volume. turn the dual mesh toggle on and adjust the offset and rotations to avoid the flat hair look.

at this point the hair cards are generated from hair curves where you can sculpt them, you can convert them to simple curve and modify individual hair, tilt or duplicate it. 

finally you can convert them into actual mesh. if the Random Flip UV is on, some of the mesh will have flipped UV. if Transfer Normal is on, the final mesh will have custom normal info from target surface normal.

when switch to viewport material preview, depends on the UV gird setup in Hair Texture Baking. click the corresponding number to set the UV preview area 

6. Hair Texture Baking

in the Bake Hair Card panel, click "Open Bake Scene", a new scene is created within the same blend file. you can switch back and forth from the top right drop down list.

in the bake scene, you can import sample hairs by pressing Regular, Clump, Curl button.

first select a desired UV grid layout, depends on long hairs or short hair or mix hair texture with eyebrow, eyelash and beard. then click various numbers to position the hair curves. fine tune them using geometry nodes controls or Convert generated hair for manual sculpt.

when it comes to bake hair textures, toggle the type of textures, select a folder (make sure to click the gear icon and uncheck Relative Path) choose size, format and quality, then click bake textures.

back to the generated hair cards, select one of the baked texture and you can apply them (make sure also uncheck Relative Path)

7. Hair Simulation with particle hair system

until Blender natively support geometry node physics, you may choose to convert geo hair to particle hair for hair simulation.

step1. select geo hair, most likely there are various geometry modifiers, go to "Object - Convert - Curves" this will apply those geo modifiers and make the hair individual strands instead of generated ones.

step2. go to object data tab, under surface-surface, use the eyedropper to select the target head mesh.

step3. go to "Object - Convert - Particle System", now you have particle hairs on the target head mesh, you may need to adjust the hair strand shape and/or decimate(rekey) hair strand point count for faster sim. 

step4. set hair vertex weight. higher the amount, less the physics effect. at 1 (red), physics does not have any effect. adjust various physics parameters and make dynamic hair simulation.

if you have any questions, please send me a message.