I run into a similar problem, having the thick dark brows. I've been known to just shave them off- and will probably be doing so again this Halloween- but in the meantime, a few tips that seem to work ok for me...
Threading or regular waxing. I don't do it, but I don't really cover up my eyebrows that much. Waxing and sealing seems to only work if you don't have to deal with too thick an eyebrow.
Spraying a brow brush with some hairspray and shaping them seems to help, as well as brow set. Once your brows are in order you can pat on foundation and powder to lighten them and pale them out. It won't make them invisible, but it will get it closer without having to shave or use prosthetics.
HTH.