I am reworking a wood pattern for greensand with 62 inside corners—-where three planes meet at right angles. Getting any material I have tried so far into those corners with a nice smooth finish has been challenging. I have tried Bondo, POP, latex caulk (too soft an no easier), and Famowood. (Wax from Freeman is on the way but not here yet). I will soon be making a scaled up version of the current pattern. So, getting the inside corner problem figured out is important to me. Bondo has worked the best for me so far. Up til now I have ended up tediously sanding those corners with 220 waterproof paper to eliminate any sand-grabbing irregularities. However, tonight I tried applying the stock Bondo with my finger as smoothly as possible, but then doing a finishing wipe with my finger wetted with 70% isopropyl alcohol. That made a huge difference. (I also tried acetone but I think the alcohol worked better for me.) No more micro-ridges of Bondo and a nice smooth fillet that will not require sanding other than just a light hit with 320 prior to lacquering. Do other people have similar/better tips and materials for inside corners? Straight inside corners at the intersection of two planes seem to be relatively easy with almost any fill material.