We liked the small pneumatic die grinder for grinding the welds, but we have a pretty big compressor for a house. If you go that way, stick with the 3M rolloc discs. 24 and 36 grit. 50 if you want to do fancy finishing. Donovan, please give him better advice if you disagree.
You pretty much nailed it IMO Jared. I will say this tho:
As the guys have suggested, invest in a couple good spot weld cutters, some Roloc discs in both 2” and 3”, in 36 and 60 grit varieties. I find using a purple 3M Clean N Strip wheel on the suspected spot weld areas first helps locate them. Usually the spot welds are slightly recessed from the surrounding metal, so hitting the spots where you think there might be a weld will result in the surrounding area going down to clean bare metal and leaving the weld with paint in it. Makes it really easy to locate the center of it that way.
I also sometimes use an 1/8” drill bit to make a depression in the middle of the weld first, this helps get the spot weld cutter started and prevents it from walking all over the place on ya.
Even with using a decent spot weld cutter, you’re almost guaranteed to run across a couple stubborn ones that still won’t separate. My advice here is to take your time and try to split the remaining weld with a thin sharp metal chisel. What you don’t wanna do is tear the sheetmetal, because then it becomes a bear to try and fix. Resist the urge to go nutz with a chisel blade on an air hammer, trust me on this.
Once the pieces are separated, do a little cleanup straightening of the edges with a hammer and dolly and you’ll be good to go. If you’re REALLY successful in splitting the pieces apart, you might even be able to reuse the old spot weld holes for reinstallation, but I’ve never been that lucky.