You only need to clean the flash channel with a 1/8 inch drill bit. Dont run anything rough through the flash hole. There is no need to scrub the hole. All you are doing then is wearing out the hole faster. Every time you fire a load the hole grows a tiny bit but at the same time the channel fills with a little more carbon. The carbon can get very hard and appear to be metal. Just clean the channel within 20 shots and you are fine. Make sure you can see light through the hole and its fine.
