What i'm wanting to do is minimize the rust coming back. Re-done the seams so they are 100% tight, but my boot rubber is a piece of shit. To be honest. So i'm wanting to spray some rust prevention mixture in the boot / pillars / fire wall (yes the car is just a shell atm) and i'm wanting to do it with the best compound known to man.

Anyone had experiance with what to use? I'm hoping there is a mixture that can be thinned and put in a spray gun hopper so i can crank my compressor up and get it into all the little nooks and crannies. So far everyone says 'fish oil'.
Recommend me something!
Cheers.