We occasionally get questions about internal rustproofing on steel frames. Should you worry about internal rust on your new, or used, frame? The fact is that the vast majority of steel frames never get any internal rust proofing treatment, yet last for many many decades. On the other hand, you'll occasionally see a rusted out frame, particularly in regions where road salt is used. So to be on the safe side, I rust-proof all my new frames. You'll certainly want to rust-proof any frame as nice as a VO frame.
A single can will do several frames, and application takes only a few minutes. The included directions are pretty good, but here are a few photos of Scott rust-proofing a prototype:
Back in the day I simply sprayed WD40 into the frame, but today I prefer Frame Saver. Frame Saver is designed to get into the smallest spaces in your bike frame and leave a protective coating when it dries.
First, spray Frame Saver into the main tubes through the BB shell, head tube, and seat tube. Rotate the frame and shoot some more in to better coat the tubes. Next, plug the tubes with rags or paper towels.
Now shoot Frame saver into all the little vent holes. There should be a vent hole in every small tube; it's there to let out gases while welding the frame. Some cyclists plug these vents with little bits of wax, but I'm not sure if that's a good idea.
Now spin, shake, and gyrate the frame to distribute the Frame Saver and coat the tubes. You need not be quite as aggressive in this as Scott. After a few hours, remove the rags or paper towels and let the excess drain out. Wipe up any that's leaked onto the paint. Repeat with the fork. That's all there is to it.