Davem is right about brake cleaner. It works great. HOWEVER, you have to remember that it works almost too well. It will totally remove any protective oil embedded in the pores of the metal. After cleaning, you need to replace that thin layer of protection.
My personal way of doing that is to blast away with the brake cleaner then use an air hose to dry the parts. An air hose gets into the tiny crevases. Then, I give it a shot of lubricant (ordinary CLP is my go-to stuff). Then use the air hose to blast off the excess lubricant. The air will appear to blow it all off but in reality it will leave a thin film on the metal - enough to protect it from rusting. Lastly, use a tiny dab of thicker lube on the moving parts before putting everything back together.