Here's a video about cleaning a freewheel to give you some idea. http://www.youtube.com/watch?feature...=eDdSpIPt5qkru

I actually don't think the process he uses is the most efficient and effective, though. I would dunk the freewheel in solvent for some time and then brush off the entire outside first (gloves are a good idea). Then lower back into the solvent and back out repeatedly, spinning (carefully) to help flush out debris and old grease. Then feed in oil at the small gap between the center and the moving portions, spinning again until it is quieter and the oil comes out the other side. I prefer putting the oil in from the front of the freewheel, as the rear gap is larger and therefore allows debris to flow out easier. Use a fairly heavy oil so that it stays in better. DO NOT use any type of grease, including spray grease.