I remove teh wheel from the frame and lay it horizontally across my lap. A piece of terry cloth, dampened with mineral spirits can be run between cogs. Pull the ends of the cloth back and forth using a "sawing motion" to alternately spin the freewheel, then clean the new position. It's easier to do than explain. Once you see it, you'll understand.

Finish with a clean, dry piece of terry cloth.

Use an light weight, spray-on oil on the cleaned surfaces to prevent rust. Alternatively, a light oil on yet another rag, run back and forth with that same sawing motion, also works well.

I unscrew the chainrings from the crank and clean them in a flat tray using a tooth brush and mineral spirits.