Don't let it dry; it's not milk any more if you do. I pre-punch stacks of patches which I store in prescription containers. I add lube just before heading to the range by squirting a dose of detergent down the inside of the container full of patches, (you could use moose milk for this) then fill the container with water, and squish the stack of patches a few times to squeeze out the air and work the soap/water mixture to completely wet the patches. At the range, I take out a few at a time and squeeze all of the water I can out of them before loading. There is no danger regarding wetting your powder doing this. The barrel is effectively wiped clean with each load, and I have never had to clean my gun between rounds. For any situation when your gun may need to stay loaded for an extended period, (hunting?), a greased/oiled patch is fine because you most likely won't shoot more than a couple of rounds.