I have a character in a sketch that needs to look very greasy and dirty. I'm thinking of using baby oil and a little ground up charcoal.
Does anyone have a better suggestion?
You can use regular black greasepaint thinned with baby oil as well. I've used cornstarch thickened and dyed to make slime, mud, grease (when translucent), and assorted goos. To make powdered make up shiny again, you can apply a bit of glycerin on top. For rub-proof make up, PAX paints can be made rather translucent.
In terms of dirt remember that grime comes in colors besides pure black. Dark browns can be effective.
------------------
Jeff F - Moderator
Magic and FX
Amazing the Masses
have fun!
he he, dont be mad, get glad 
------------------
"I am Mars, the god of War, and i'll cut you down".
All times are ET (US)