might dye seats (not spray paint)

[twofortyesecks]

Howdy, I just got some S14 seats for my S13. They are the gray seats, not the black with the pattern. They are reasonably clean but I want them better. If I dyed them black it would look a lot better. I used the spray can fabric dye from Autozone on my headliner (it used to be tan) and I don't like the stiffness of it, also it rubs off after awhile. I was looking into acid dyes and I was wondering if anyone has used them. These are the kinds that you mix with some vinegar (I think) throw in the wash machine with what ever needs to be dyed and its supposed to be super permanent. Will this dye screw anything up such as the wash machine? Also how hard is it to make it come out even? I can't imagine too hard it is jet black.