Hey everyone! I made this tutorial in order to archive how I did the fur for a commission piece. It took some research in order to get it right. Primarily, I studied how Clockbirds does her pieces (she's a very talented artist on youtube and Deviantart!) so credit to her for letting me try to figure out her technique. She uses a different program, however, so I came up with a formula that I can remember and use on Clip Paint Studios!
 Base Color/Choosing Your Colors
Here, I already have my line art and base color filled out. The commissioned character is a Neko boy, so the tail is a long-furred cattail of cream color. I usually pick out my colors before doing my brushwork, and even if they're not of correct saturation or intensity, it's alright since I can adjust those later.
The character's original color is a lot lighter than the base color I'm using, but for fur, I learned that coloring tuffs from dark to light works best.
Here I have: [center to left]
Mid Color (the center color, a more saturated orange color)
Highlight Color (original color; a lighter, yellower hue)
[Base] Shadow Color (a slightly unsaturated darker color, towards the red spectrum)
2 bonus colors of orange-pink, unsaturated hues for uncoat subtly. (Yes, they are orange, not purple or pink! :D)
Since I normally do everything on one layer (for the sake of recreating this tutorial, I put the tail on another raster layer), I use the wand tool to keep all the fur brush work inside the selected area. That's just me, however; if you separate all the clothes and other pieces of the picture onto different layers, you can just use the "Lock Transparent Pixel" tool to keep your work within the line art. ^u^b
Using the Soft Airbrush Tool, I create a gradient around the tail, using the undercoat colors.
 Brush Stroke Technique and Tools
I then use a combination of "Dense Watercolor" and "Paint and Apply" brushes to texturize the tail. The Dense Watercolor brush shapes the gathered tuff of fur, and the Paint and Apply blends the end together with the base colors.
I go over the tail with the Medium Color of bright orange. Try to keep the brush strokes short. Also vary between thin and thick chunks of fur.
Once you've finished the with the base colors, go back and repeat the same steps using the highlight colors! It looks complex, but really, it's just a simple texture! :D
I personally went ahead and made the darker areas more defined by using the same method of Dense and Apply brushes, with the shadow color. After fine-tuning the random strands, I use the soft airbrush to give the whole tail some 3-dimensionality.
At 31% I used the multiply mode, and then rim lighted the tail with some of that undercoat color pink-orange, using the overlay mode.
Final touch; I mess around with the brightness and contrast, levels and other color edits to make it pop!
And it's done! :D
I also made a speed paint out of this commission, so for those of you who'd rather watch the visuals, you can watch it right here! Even though the footage is sped-up, hopefully, it might be easier to understand. Thank you very much for checking out my first tutorial! :D