About three years ago my parents removed tore down their bathroom wallpaper because they were going to remodel. They never actually got around to remodeling so the walls in the bathroom have just been exposed drywall.

I just visited my parents in Southern California(I live 3,000 miles away) and was surprised to see that a lot of mold was growing on two of the bathroom walls, about 10 or so square feet. I am guessing this is due to moisture from showers not being properly ventilated.

Next time I am out there I can install a more powerful ceiling fan and see if that helps, but how can I get rid of the mold that has grown on the surface of walls (and maybe even deeper). Their home owners won't cover remediation and I don't think I can take out and replace the affected dry wall by myself. Once I have removed the mold is there a paint I can use on the walls that well help prevent the mold from coming back?

Thanks for any advice.