working with actual rust is a pain, because you can't just use any clear coat to seal it.
you pretty much have to use automotive clear coat. it's generally made for being able to seal rust spots--which is tricky because you have adhesion problems with most clear coats (the rust tends to powder or flake off, so you end up with bubbles in the clear with most clears).
and you obviously don't want to leave it fully exposed because then you get rust all over yourself as you play (which is dirty and not particularly healthy either).
I have graduated as autobody repairer and have worked in car paintshop so i have the skills and knowledge to do these things.