Is there any better way to draw editable tattoos on animated objects then using Decal?

Assuming easiest scenario?

I would look into mesh overlay if i were you. Decal is not the right way to do it.
I dont have an example but there might be a tuto on it

You can see theres drawing with animated skel as well which should make it easy to set up fitting your character

MeshOverlay will create a new mesh, which is not good for this scenario.
I think void MeshPart::drawOverlay can do this, but if I remember correctly it will generate good results only in deferred renderer.