Believe it or not, some guys put the wood in the top rack of a dishwasher. You can also put the parts in an oven at a very low temperature setting.
Gasoline removes cosmoline very well, but can be dangerous. You may want to check out surplusrilfe.com for some tips.
Cosmoline is just a part of the rites of surplus rifles. Good luck and enjoy your new rifle.
If ye love wealth better than liberty, the tranquility of servitude better than the animating contest of freedom, go home from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains set lightly upon you, and may posterity forget that ye were our countrymen. ― Samuel Adams