Hard to beat break free poweder blast to clean it, then a good coating of break free CLP to protect

CLP
http://www.break-free.com/?location=/products/index.asp

CLP is the single product out military uses to clean and maintain weapons. CLP is far superior to WD-40 and rem oil. I buy it in the 12 oz size and use it in all of my firearms, including muzzleloaders.

for longer term storage (>1 year) take a look at the Collector Liquid product. It is speced and >5 years storage time on firearms.