I've done the following a couple times, with good results:
1) Using a bunch of paper towels, I wipe off as much of the cosmoline as I can.
2) Completely strip the firearm, so that the metal pieces are separate from the wood.
3) Using a "pasta pot" (a huge kitchen pot with an integral strainer), I heat up several gallons of water.
4) Place all but the largest (barrel assy) metal pieces into the water. Let them "cook" for 15 minutes or so, and then remove. Place on several layers of newspaper to cool.
5) Soak both ends of the barrel for 10 to 15 minutes each, remove for cooling.
6) When the metal pieces have cooled sufficiently (ie. still slightly warm to the touch), clean with Hoppes #9 and wipe with a very lightly oiled cloth.
7) The barrel should be OK on the outside, but may require some diligent scrubbing to clean the bore.
8) For the stock, I wipe down multiple times with mineral spirits and then finish however I want. This won't really get rid of everything, so I'll lay the stock outside in the sun during a few of the warmer summer days, to let more of the gunk leach out. A heat gun or blow dryer would also work, but I'm lazy enough that I prefer to let the sun do the work.
BTW, using the above method, I've cleaned a 1903A3 which was a complete mess in about an hour and a half. That got the metal pieces quite serviceable. I let the stock dry until the following morning before I reassembled it.