I've got a long bottle brush that I`m thinking of using to clean up the worst of the build up. I like your idea of using a weight to knock crude loose where the brush can't reach, though my problem would be freeing up the piston when it's stuck in the open (deployed) position. There's not much room to get leverage against the front of the piston when it's jammed in the forward position (especially with my smaller 13mm Ecee). Looking forward to your build. I agree with Dave, I'd definitely recommend using a 1/32" or thicker plywood disc in addition to JB Weld on the ejection end of your balsa piston, or consider substituting a 'glass coupler in place of the balsa, as I'd think it's way more heat resistant and less problematic in the long run.