Here is what I did.
Disassemble the rifle and bolt.
Make a mixture of Simple Green and Hot water. If you can't find Simple Green, look for Mean Green at a dollar store.
Soak the metal parts in the solution, and scrub with a toothbrush until all the cosmo is gone. For the barrel, poor some of the solution down it, and scrub with patches, make SURE you dry well afterwords. I also like to scrub directly in the chamber a little bit with a patch.
Dry everything really well.
For the stock, I did something simple. I laid it down, and heated it up with a hair dryer, when cosmo came out I would wipe it away with a paper towel. When the stock doesn't feel all gunky reassemble and go shooting.