I'm guessing you are talking about inlines...I clean betwee shots, plain and simply...It's not really a good idea to throw a load of black powder down a barrel before you clean anyway...I just have a small container of alcohol, cleaning patches and oil in a vest pocket...It only takes about 3 minutes to clean, lube and dry the barrel before the next shot.

With my flinters, I use a .018 patch for the first shot and .015 for second...