Auto body repair & detailing: rust proofing, rust buckets, drainage holes

Question
Is it a good idea to enlarge or even add additional drainage holes in the bottom of doors and other water pooling points? Other than expensive commercial products, is there an effective rust proofing coat that can be applied to body panels and frame componants prone to rust? What can you do to stop existing rust? A friend told me to wipe used motor oil on everything but I'm concerned about the environmental implications...

My second question may be a little harder to answer. I've been thinking about "improving" the rear gate design on a 1991 Toyota 4runner. It's so stupid. Hinges are on bottom and a motorized window opens upward out of the gate. The whole line should be declared marshland by the EPA because if anything else collects rainwater like this, I'd be amazed. And if the motor on the window goes kaput, you can't open the door...Toyota job security I guess. Have you ever heard of anyone using a gate from a comparably sized vehicle that opens from the top, with a nice push button window that opens on hinges as well (so water can go into the river where it belongs)? Besides ensuring a good fit and relocating the hardware, would there be any issues that would not make this a good idea?

Answer
CLEAN motor oil can be used to help inhibit the spread of rust. Dirty oil stinks, and if you don't want that crap in your engine, why would you want it in your doors and such? It's contaminated with all sorts of garbage, even water. Don't go fooling around drilling bigger holes, you will actually bare the painted steel and give rust a place to take hold. 1991 toyotas were RUST BUCKETS and the only thing that can save this veicle from rusting is divine intervention, or move to the Sahara desert. Be sure to leave during any rainy seasons. If you are willing to spend about 5,000.00, someone might spend a couple months modifying the entire rear body on your 4 runner. It just ain't that simple, man. It isn't like a door on a house, all nice and flat. Every gate has curves, angles, and seals. Not impossible, but not reasonable, either. It would be silly to wast the time and resources on a 16 y.o. truck. you are fighting an uphill battle, my friend. It would be easier to put a blazer body on the chassis than to modify the existing body. I know, the Toyota's run like mad, but the bodies just don't hold up. Bill