I've watched people who own a certain cult vehicle that is notorious for seam rust try everything except the really nice $250,000 backpack laser units...
a Fein multi-tool works well
some say this:
https://www.homedepot.com/p/WEN-Rotary-Tool-Kit-with-Flex-Shaft-2305/203604481
with a thin saw blade and/or think disc grinder type tool is 5x better than the Fein
others like an airbrush or pinstriping brush with silica sand blaster setup
one of the above must be best... use 3M 8310 seam sealer afterwards
I've never heard of anybody use vapor blasting, but...
https://www.youtube.com/watch?time_continue=37&v=xfczxBWJuNg