I have several rusticated Peterson's that I love. The problem is, being fairly new to this, I neglected to wipe the rim of the bowl after each smoke and now have quite the gunk buildup. Does anyone have any suggestions on how to clean this without damaging the finish? I have another smooth finish (much cheaper) pipe and I was able to get that one cleaned up nice. The nooks and crannies in the rusticated pipes make this a little more difficult and I'm scared to scrub with anything other than a soft cloth.