you mentioned your welds being messy, are you using flux cored wire? flux cored wire is usaully not allowed in the body shop business because of the contaminants(flux residue)creating a rust through problem because of the acids in the flux and the possibility of an adverse reaction to any fillers you may use.If you are using gas as a shielding agent, you may not have your regulator set right(enough flow to shield the weld), your material being welded may not be clean enough(rusty metal will pop and sputter and leave a huge mess,blowout and look crappy)I also use a piece of copper or brass behind the weld as a backer for the hole. the weld does not stick to the brass or copper and it allows you to fill the hole without it blowing out. something to think about
