LIE as you can add the skin texture back over the tattoo at a very low opacity so it looks like it is under the skin whereas Diffuse Overlay does just what the name implies overlaying ontop of the skin making it better for make-up.
Also, you may find that you'll need to add the tattoo (or a slightly modified version) on other layers. For instance for the face tattoo, if I didn't add it to some of the subsurface channels as well it looked very washed out. That's where LIE can really help as you can add the same image (or modified ones) multiple places. I write down the location and size settings from the base diffuse channel so I can make sure they line up on other layers.
Comments
LIE as you can add the skin texture back over the tattoo at a very low opacity so it looks like it is under the skin whereas Diffuse Overlay does just what the name implies overlaying ontop of the skin making it better for make-up.
Also, you may find that you'll need to add the tattoo (or a slightly modified version) on other layers. For instance for the face tattoo, if I didn't add it to some of the subsurface channels as well it looked very washed out. That's where LIE can really help as you can add the same image (or modified ones) multiple places. I write down the location and size settings from the base diffuse channel so I can make sure they line up on other layers.