A lot of Evasive Angles' titles feature this - off hand - the Big Bubble Butt Cheerleaders, Big Butt Smashdown, and Big White Wet Butts series all feature the girl getting her ass oiled in nearly every scene. Elegant Angel's Big Wet Tits series also features this (tits oiled).

If you are looking for a more all body oiling - a title that I have in my collection - Crude Oil - is pretty good.

I'm a fan of the oil scenes myself too.