Thanks for the help all.
How picky do I have to be with cleaning it?
Is it a general wipedown with a cloth to get the cosmo out or (figuratively) power washing the crap out of it so that it's all bone dry before I lube it?
IMO you need the bore, chamber, gas cylinder, bolt internals spotless and free of cosmoline. The trigger group, op rod, receiver raceways need to be pretty clean and lubed as well or you're asking for trouble. That cosmo is like wax and it often contains grit and metal particles. Use a solvent.