Body work soldering/leading

If its just screw holes mig will fill those in a dash, just work fast so its doesn't blow through. Up to about 1/4" is easy.

+1for JB weld as a chemical metal filler/profiler, it's superb material and have used it for years...even repaired a 4.2ltr XJ6 engine sump with JB and it's still running strong 17+ years later.

The other option here is to braze-weld using low temp alloy rods. These are readily available from eBay etc., and the weld infills properly/does not fall out/provides a proper 'weld'. The key here is to ensure the parent metal is spotlessly clean...buzz back, thoroughly clean off with methylated spirit, heat dry, then braze-weld. When using to fill larger holes you might try taping a blocking piece of the rear of the panel to stop weld falling through. On box sections, build up weld as per normal mig/tig. I even used these to weld alloy breather necks to alloy oil filler caps on v8 engines

https://www.ebay.co.uk/sch/i.html?_...0057.m570.l1313&_nkw=alloy+weld+rods&_sacat=0

Whack a bit of coathanger in as you mig the hole...practice on some scrap steel with holes drilled to same size first...