I suspect the fact you were welding 18's gauge to practice on is part of the problem, thicker metals are easier to get pretty welds on as you are less likely to burn through.
What I would suggest is you get some steel the same thickness as the bodywork (probably 22's gauge could be 20's....) and set the welder up on that.
When you get good welds then have a go on the car, if the metal is even slightly rusty you are going to struggle (and shouldn't really be welding it anyway, rusty metal belongs in the bin)
What I would suggest is you get some steel the same thickness as the bodywork (probably 22's gauge could be 20's....) and set the welder up on that.
When you get good welds then have a go on the car, if the metal is even slightly rusty you are going to struggle (and shouldn't really be welding it anyway, rusty metal belongs in the bin)