Also, 80 grit on a DA works well on surface rust. Time consuming, but it doesn't heat up enough to wharp anything. Bad pitting would have to be spot blasted, then etched and filled. I use short hair fiberglass, as it is permanent, but goes on like plastic. If you etch it afterwords, it will hold up fine under epoxy primer. I did a hood this way 3 years ago, it still looks like I just did it. Maine sucks humidity wise, it is like Florida, only COLD all the time. But as long as you get rid of the rust it won't come back to haunt you.