http://wh40k.lexicanum.com/wiki/Mortifactors
According to wiki they are just black and bone color ultrasmurfs, any place with skull transfers would do, though they may come in white, you'll just have to paint over it with bone. For the scouts, you can paint some tribal tattoos on the flesh. Maybe some Tyson face tats on some veterans too.
Artemis, the deathwatch captain apparently is a member.