Quick tips on stopping the rust on the cheap

This would be an easier call if we knew what sort of tools you have.
Grinders,drills,as mentioned compressor and air tools.

Grinder to aggressive and would leave you a mess to deal with.
Flapwheels and discs would work,in an electric drill,also a variety of wire wheels.
They all leave their own marks behind, how you want to deal with them is a matter of tools.
Could just soak a few rags with evapo-rust and lay them on the panels for a few hours and it will somewhat neutralize the rust.
Clean up,degrease,scuff with scotchbrite and apply a coat of etching primer followed with your favorite flavour topcoat.