I just use Sharpies for mine, metallic silver, gold, and black, mostly. I've had an alright experience with these, but they seem to be oil based? It takes some encouragement and a couple passes to get them to coat the entire seal, especially if it's a big, solid shape. It does smudge at first, but if you give it like 20 minutes to set and dry, it seems to last quite a while. I've got it on a seal that's on a character journal that I cart around to tabletop games all week, and it's still holding up great.