[BIGglaSS]

Excellent, keep at it!

If you already know this, sorry, maybe someone else will find it useful. Quit looking at it from the point of view "building up heat". Go back to my 4 simple rules. Heat = shrink, hammer on dolly = stretch, hammer off dolly = shrink. Pick your method. If you break it down to these simple rules, it is easier to manage sheet metal.

Heat Affected Zone (HAZ), the end result (when cooled) is shrinkage. It is going to happen, and you're gonna have to fix it. Those are areas that need to be stretched when you're done welding. If you're gonna weld, heat happens. Sometimes you can plan to cut/weld to place the HAZ near a structural feature. Guess what? It still shrinks. The adjacent structural piece holds it in place so you can't see the shrinkage, and you may not have to fix it. That's why making a weld seam across the center of a door or fender turns into ocean waves. There is no structure to hold it in place.

When I "build up heat", I get a blowout. Otherwise, weld on... The other problem to "building up heat" is when you are welding and the surrounding metal is hot, it is expanded. If you weld in that "built up heat" condition, you can inadvertently lock in the "expanded" area causing lots of heart ache.

That is the reason for skipping around to keep from "building up heat". So you are welding on metal that is NOT currently heated and expanded. draven's technique works great, and this is the "why".

If you learn to torch or TIG weld, you can actually see the expansion of the metal as you weld.

Anyway, ponder on this and move on.

Finish welding up those seams. "All Metal" is not the be-all end-all to filling. Remember science class? Two dissimilar metals makes a battery. Steel and "all metal" can create galvanic corrosion, causing future failure. Your best solution is keep chasing pinholes with the welder until they are all gone. Lightly blast welded areas, and paint with epoxy primer. Then use a high quality filler over epoxy. The repair will be waterproof.