This particular situation isn’t exactly a cover up but a lot of the same principles hold here. Sometimes one of the best things to do is make sure your light sources and shadow shapes look correct. Pushing contrast in those areas can help to reduce the amount of work needed in some of the other areas.
If the tattoo you’re trying to rework looks a little flat or messy then there’s a problem with your hierarchy of shapes, values, and colors. Pushing contrast in the foreground can really help to pull the subject forward. Bumping up lines or edges and darkening or redefining some of the shadow shapes can really help to define the image more clearly for the viewer.