Spot welding works for me it helps clean the metal and you can use the previous spot as a heat sink to start your next spot. Clean as good as you can but some stuff just has to be cooked out to clean. The heat from the previous spot can help with that. Also if you burn through don't try to fill it in while its hot. Let it cool then come back use the previous spot where the metal is thick as a heat sink. Add a quick spot then weld somewhere else and come back after it's cool. Repeat. Check out Fitzee's Fabrications on you tube.
