With netal panels you just gotta do it very slow with the power tweeked abit and spot weld rather than trying to seam. Ive made a balls up on my rear arches as i spot welded about and inch at a time between cooling and i can see the panel has destorted abit so i might pay a pro to get the rear quarters flat again.

Painting is easyier with a gun as it lays paint more evenly and less likley to run. The jey with getting paint to look good is prep, prep, prep, a bit more prep, prime, smooth primer, paint, let go hard over a few days, flat back with 2000 wet, clean thourghly then, laquer, 5 days or so later machine polish with soft head and smooth compound them hand polish. Missions but worth it.