Whenever you shut off your water, little particles will flow downstream and can potentially because small leaks. I like the idea of flushing, but flushing before the cartridge is inserted. This takes timing and communication, using two people. One at the outside shut off valve, and one inside to collect the water before it gets behind your wall. I'd recommend you shut down the water, remove the cartridge, inspect for any tears, flush for 10-15 seconds, lube up with O ring grease and reinsert the cartridge. Don't forget to inspect the springs and seats for wear (if applicable) while the cartridge is out. Lastly, using some O ring grease on the threads of the bonnet nut allows for a tighter cartridge, which in itself may stop these small drips.