I keep an air gun handy and quench it for a couple let seconds between "stitches" if needed. I always fit my patches to butt against existing metal with no gap. When you are working with 20 gauge it's easier than filling in a gap. Also use .032 wire.
Sounds like a project for custom made panels on the English Wheel. Small non structural areas could be leaded over. Been a restorer over 40 years and still haven't found the majic bullet.