Never use acetone to degrease feathers or fur prior to dying!! It distroys protein molecules.
When dying feathers or fur (including tails from various animals we use in fly tying), add some clear Ivory dish detergent, venpol (available from Veniards suppliers) or Synthrapol (synthrapol was formulated at both a degreaser and a dye dispersent specifically for dying and as such is the best degreasing agent to use) into the dye bath. This degreases the material being dyed and helps keep any grease suspended in the dye bath, which promotes even dying and vibrant colors. Synthrapol is by far the best degreaser to use because its dye dispersent properties prevent splotchiness and thus helps produce nice, vibrant, even dye results.
Dyes to use for feathers and fur should always be acid dyes because they are colorfast is water, Koolaid is not colorfast in water and will wash out with use. REmember that the acid needed for dying is nothing more than common household white vinegar, which is hardly a toxic substance.
Brands of dyes that are readily available in the 1 once or smaller quantities home dyers of fly tying material need are: Fly Dye (one of my favorites, with colors described in normal fly tying terms); Veniard (some colors are unpredictable; but hot orange, fl. pink, and Kingfisher blue are some of the best you can get); Jacquard ( my other favorite, and it is available at many craft supply stores around the country); and the dyes sold by E. Hill Co., Inc (a fly material supplier). There are other very fine acid dyes on the market but they are harder to locate unless you go to the manufacturer and buy the minimum 1/2 pound or 1 pound of dye manufacturers require you to purchase (trust me, a 1/2 pound of dye would be like the average fly tyer buying 4 pounds of marabou in one color!!).