Well, with a flick of the brush, your painting could change. For strand-like materials, like hair or grass, on watercolor and similar types of painting, I just kind of paint when the hairs on my brush are a little separated. For oil painting, I just draw some strands, and I change the tones around to make it seem like there are more "strands" than there actually are. For "smooth surfaces", I blend everything together. If you don't know how to blend paints together, here's how.
1. You find the color that you want to make.
2. Classify it as one of the primary, secondary, or tertiary colors (red, red-orange, orange, yellow-orange, yellow, yellow-green, green, blue-green, blue, indigo, purple).
3. Decide if your color is darker or lighter than the paints you have - if its darker, add a tiny bit of the complementary color, brown, or black. If it's lighter, add white, or use a lighter color.
4. Mix your tint/shade with your primary/secondary/tertiary color. Make sure that your paint is not just a bunch of different colored spirals. You should not be able to pick out a color change between one side of the paint from the other, if that makes any sense.
5. Apply your color to your canvas, and use even strokes. Go over the area of that color with that paint about 2-3 times. It usually works.
6. If you want to blend that color into another color, just add that other color into your paint (unless if it's complementary. In that case, the "middle tone" would be brown that slowly fades to the other color).
Sometimes, I have to do layers upon layers upon layers for oil painting to get the texture right. In those cases, I don't really worry about one spot more than the next, because if you just focus on one spot, it might turn out that there is another layer on that area, which would be horrible because then you would have to redo everything. You should also plan out the order of your layers so this doesn't happen.
Another thing for textures is roughness. For roughness, I just kind of "dab" my color onto the canvas and put a bunch of its tints and shades around it.
That's it, FOR NOW!
And have fun drawing your textures! If you have any questions, please comment!