I have had a DVD on this subject for a few years but never really got round to watching it fully. It is called " Bodywork Restoration Tutorial" and the chap doing the magic is called David Gardiner. What he has done in his time is mind blowing. Anyway I have got to the welding section and a few points he made was mind blowing, to me anyway. He was demonstrating gas welding and at no point did he use filler rods. It was all done with the flame and skill. Then he turned to tig and again he did not use rods. He also made the statement that tig is no good for ali? He then went on to mig and he reckoned that it tends to warp the sheet where the other two dont! I dont know if it still can be bought but if it is it is worth watching. His panel beating technigues are great. Mind he has all the equipment like dollies spoons etc.