Alright, here's what you do. Get a few old t-shirts, a punch set, and a screwdriver.
Step 1 - set it in the sun or in a warm place. The warmer that stuff gets, the easier it is to remove.
Step 2 - wipe off all the excess. It WILL come off - by itself!
Step 3 - completely (and I mean COMPLETELY) disassemble the rifle. Wipe the excess grease off of everything, and be prepared for a metric fuckton of that shit underneath the receiver and handguards.
Step 4 - liberally spray EVERYTHING with your CLP of choice. Then, wipe it off.
Step 5 - apply normal amounts of CLP and put everything back together.
Step 6 - when you first take her to the range, bring an old t-shirt with you. After about 20-30 consecutive rounds, cosmoline will leak out from wherever you missed it. Use the t-shirt to wipe it off.