1. I use Chartpak markers for nips and labia myself. They’re Xylene-based which is a TPE solvent, so it sticks to TPE really well. I colored the nips and labia of my WM doll over 2 years ago with Chartpak marker and it’s still there even after several washes and baby oil treatments and I’ve had zero adverse effects! But at least one member reports adverse reactions when applied to his doll.
2. I use a washable marker, dab off the excess, and go over the nipples with eye shadow. Same for lips but with lipstick.
3. Personally, I like to use powder makeup and fix it with vaseline. Apply the makeup with a small brush or makeup applicator then dab a tiny bit of vaseline into the nipple and carefully rub it in (TPE dolls only). After leaving to dry, I find the color lasts for a few months or more. Lipstick is best applied with a small makeup brush and once dry clear lip gloss can be applied to give it a shine.
4. If you want glossy lips, you can mix a little clear lip gloss with the lipstick on the brush or applicator.
5. For the nipples, I use “275 crazy for coffee” lipstick. it looks great on all skin tones. I draw it on and then I put a makeup removal pad in my palm and just press it against my artwork several times until I reach the desired tone. just press or dab with your palm do not wipe around. For the lips, I try to stay with a matte style lipstick. I still haven’t had success with glossy stuff but I’m sure somebody on here has a solution for that.