Remember that unbleached PFs will effect the final color, so take that into account.
Many craft/fabric stores i.e. Joanns sell the same kits you find at Dharma, which are by Jacquard(a producer/distributor of all sorts of dyes). Procion dyes are a class of fiber reactive dyes.
A similar product is Dylon Cold Water dyes which are also fiber reactive dyes and work in about the same way as Procion dyes. I have never used them so I cannot say they are better than the tie-dye kit, but they are an option. Quite honestly, procion dyes are pretty simple themselves

Good Luck!
Kathy