One thing I forgot when you are repairing metal in an area pay attention to whats behind it because once you close it up the opportunity to remove surface rust is gone, so take the time to remove any surface rust that might be a problem.
There is an excellent disk to use on your side angle grinder to quickly remove rust, paint or debris from metal and it is non destructive so it won't remove any material from the sheet metal.
Polycarbide disk
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