Hello YoungForge,
I like to use small water color brushes. I do most of the work with a small round brush. An expensive one would be under five bucks. I generally thin the color first I am going to paint with by taking a very small amount on the end of a paper clip and put in a small medicine cup. Then add a few drops of a solution of 50/50 rubbing alcohol, highest %/ demineralized water and a few drops of glycerin. (All these things can be found at your local walmart. The alcohol and glcerin are pharmacy items.) By adding more and more paint you are able to achieve a range of color from transparent to opaque with any water based acrylic paint you like. Paper clips and needles are good for dots and spots in a range of sizes. The rest is really up to your imagination. Best regards.
Vic