(Original Tutorial in French)
http://yaoi.y-gallery.net/view/637757/

I thought I'd share the basic tutorial in English, for those who can't read French.

Things you need:

Preferably Photoshop CS3. A Mouse, at least.

Alrighty:

Step 1 - Open CS3. Create New Image. Should be around 20 pizel square (height/width).

step 2 - Select Brush Tool. Make sure your brush is on "Hard Round 1" style before drawing your 'brush' style. Try to imitate the "Dune Grass/Grass" brush that exists in your brush styles. I went with two strokes in an )( style.

Note: It will probably take a couple different brush styles that you make before you settle on something that looks good to you.

Step 3 - With the brush style drawn, go to "Edit" then scroll down to "Define Brush Preset..." Name your brush.

All clear so far? If you have questions, ask away.

Setting up your new brush preset:

Click on "Brushes" (usually located on the right side with all the tabs and stuff in a default workspace.) Your 'new' brush should be located in "Brush Presets" and at the bottom of the list.

Anyway. Select "Brush Tip Shape"

Diameter should be what you scaled your brush to be (20px by 20px or whatnot) Angle should always be at -90 degrees. Spacing - whatever % you think is appropriate.

Next:

Click on "Shape Dynamics":

I have my "Size Jitter" at 100% - cuz it makes the hair as small as possible, I think. Immediately under that is a drop down button - Select "Pen Pressure"

"Angle Jitter" is about 15% at default. Experiment with the look as you go along.

Immediately under "Angle Jitter" is another drop down button - Select "Direction" (which makes it so you can sorta lead the direction of the brush in the way you use it.)

I left it at 0% for "Roundness Jitter" (I'm not sure exactly what it does since it doesn't seem to do anything obvious). Next drop down button is "Off"

That's it for this part.

Select "Scattering"

Check the box "Both Axes", and set your "Scatter" To approximately 200%. (Depends on how much of a scatter you want when you use the brush.)

"Control" drop down button just below - Select Pen Pressure. Set your "Count" to 1 or 2. (Usually 2). "Count Jitter" = I'm not really sure on this feature. Below it is another "Control" drop down menu - set at "Pen Pressure."

"Smoothing" and "Protect Texture" tabs on the bottom of this brush's settings should already be selected by default.

Lastly:

Pick a color you think you wanna use for hair, and color (I'd put it on a separate layer when you do a pic so you don't accidentally ruin it.

Color away.

Hope this helps. If you have questions... I can try to answer.