Ok here is my situation, i have a 1972 charger with the vinyl top roof, i thought i fixed it with rust bullett a few years ago but i guess that didnt work. It now looks like the surface of the moon (little poc marks all over it that have rust under them, some even poke all the way through to create a hole). Im going to get some steel grinding brushes and put them on my grinder and strip the roof down to bare metal (holes and all). I have a stick welder and a small mig-welder. How can i fix these holes for good. Keep in mind that i will be putting a vinyl top on it (so it doesn't have to be perfectly smooth. What are my options (fiberglass? welding small patches from the bottom? etc?) and how should i go about them, i dont want to replace the whole roof b/c im 20 years old and broke.

I've been successful using my MIG to fill holes up to the size of a dime. Anything bigger and you're better off putting in a patch. I put a piece of copper flashing on the top side of the roof and do quick little spots from underneath. I use the copper to give a flat finish to minimize the amount of sanding/grinding. You'll need to experiment with the settings on your welder so you don't burn through.