well it sounds like you have the tools. how long have you been welding? if you have a tig im guessing you have been at it for a while ... I am 2 years into tig and have alot to learn still and have been doing it almost every day for those 2 years .
butt weld clamps will give you less then satisfactory welds with the tig because the gap is to wide .
here is what i shoot for as far as gaps go with the tig
the butt weld clamps are made for a mig and they still leave the gap a little wide for my taste . i shave then down til they are pretty thin . but not touching . mig likes a small gap.tig likes it as tight as you can get .
never use a flange tool and never rivet a panel in . . a flange is just going to be a place for rust to start . also it takes away valuable access to the back of the weld .
wheel wells are a bit of a pain as well . tedious welding and grinding .
anything else you need dont be afraid to ask!!