Photoshop may be a photographer's best friend (after his cameras and lenses), however, it is nice to not have to spend so much time in post-production, if you can do something about it in pre-production.
I shoot lots of go-go girls and fetish models, so bruises are a fact of life...
One of my MUA's is a miracle worker with DermaBlend:
What are your Make-Up Hints/Tips/Tricks for Bruises, Scars, Stretchmarks, etc?
ADG