I'm not sure what your asking. How many shots to coat a clean barrel? Or how many shots before you need to clean?
I shoot moly in my high volume shooters, 22-250, .223,257WBY, etc. I only clean those rifles once a year, that is over 1000 shots out of the 22-250. I always shoot 10 rounds through a clean barrel to lay down some moly. Shooting over a crony, you'll see the velocity decrease a little each shot as the barrel gets slicker and the pressure goes down.