The Unofficial P64 Resource Forum

Mine wasn't as junked up as some surplus guns but was covered with cosmoline inside. Very hot water and soap cleaned it up pretty well. After the first range trip I found a little more cosmoline, so I field stripped the pistol, removed the grips and steamed it for about 20 minutes.
After both the hot bath and stream bath, I scrubbed it with MP Pro7 and let it set for a while covered in CLP, before wiping it down. The MP Pro7 / CLP bit I do to every new gun.
There are about 7000 suggested methods for removing cosmoline. Paint thinner/mineral spirits, kerosene, brake cleaner, running it through the dish washer, baking it in the oven...are a few of the less creative. But, the above worked well on my p64. Just keep in mind the grips are plastic.

Thanks, I think I got most/all of the cosmoline off manually with solvent; but there's got to be some in the trigger mechanism and safety mechanism that's still there.

Can I boil/steam the entire slide and frame of the pistol? I'm assuming that after air drying or modest heat drying (oven at 125F) I can spray the whole thing down with CLP and the metal will be sufficiently protected... correct?

Really appreciate all the help on this board.

Long as you take the grips off, and completely dry it after, hot water shouldn't hurt anything. I cleaned the firing pin channel and recesses of the slide when I had mine apart to install the firing pin spring with hot soapy water. No issues there, everything is easy to get at with the safety out, but it was a pain to put back together.
I was not able to get all the cosmo out of the action on the first attempt. For that I took off the grips and used a wooden rod through the barrel to hang the pistol across the top of a large coffee can and then steamed it with my wife's clothes steamer. Poring boiling water through the action probably would have worked just as well.
To dry the frame I wiped it down with a rag, soaked it in rubbing alcohol and wiped it down again. Rubbing alcohol evaporates faster than water and dries the water out with it. Learned that trick at Parris Island.
This worked for me, if you do a search for cosmoline online you'll find many other approaches to removing the stuff. Good luck.