I used to dye my own lashes, I think it was a 2 part dye that I mixed into a paste then applied with a stick. Might have been a one part paste, I can't remember! Anyway, it was good.
I bought what I though was the same one recently (Eyelure) and it was a liquid that I had to 'saturate' my lashes with, I assume that was the developer, then a white paste/cream that you brush on. It then turns black and dyes the lashes.
Except it doesn't. Because my lashes and brows don't absorb the liquid stuff you put on first, so the cream doesn't develop. I don't know if I have unusually waterproof lashes (washed my face thoroughly before applying, no makeup/moisturiser etc on lashes) or if it's just a rubbish product. The only thing I dyed was the skin under my brow hairs. So that was nice 
Anyone know if there is a product like the mix then apply cream/paste I used to use? I have a vague recollection of the rules being changed on the strength of home dye that can be sold - maybe it's something to do with that and they can't make it like they used to anymore?