Hot water anddry patchs to remove the powder fouling. I also run a patch with Shooter Choice MC#7 and a bore brush to remove any plastic fouling, every so often. Finish off with a patch of Sheath or similar gun oil for protection. I always run a dry patch prior to assembly or loading/firing any firearm to ensure excess oil is removed.

For the breech area I used a brush and 50%alky/50% windsheild washer fluid solution. Give it a few rinse under the tap in hot water, then wipe dry and tumble in a rag with some gun oil. I would let them stand over night before re-assembly. As mentioned use of an anti-seize grease or pink teflon tape on breech threads is required.