Although I masked the airleron ribs when I varnished them, the epoxy varnish still seeped under the tape.To remove the varnish, I made a small sanding stick from 1/4 x 1/4 plywood and attached adhesive backed sand paper on it. I started using 220 grit, but found that very slow going, but the 120 grit worked real well. I carefully removed thick patches of varnish with a very sharp, high quality 6mm wood chisel.