Next, I oiled the inside of the frame (and, well... yes, unintentionally also the outside... and my hands... and the saw horses... and my forehead...)
This should keep future rusting to a minimum and, providing I don't light it on fire, should help the grill last a good long time. I used HD30 oil.
My first attempt was to saturate a piece of paper towel, wad it up and press it down into the frame tube an inch or so, and then pour a quarter inch of oil on top of it. I then slowly pushed the wad down the frame tube with a piece of bamboo - while the opposite end of the frame was in a tunafish can to catch the wad and oil. The theory was that the quarter inch of oil would spread itself on the walls of the tube as I pushed the wad through.
It was a nice theory. What actually happened, though, was the wad got hung up here and there , eventually turned sideways, and came out the bottom *without* spreading the oil. Also, the bamboo became so slippery that I nearly got it stuck in the tube. After several tries I moved on to plan B.
Next, I poured oil down one sidewall of the frame tube while holding it an an angle, rocking it side to side. The opposite end drained into a tunafish can. I was able to look down the tube and actually "steer" the oil so as to cover the entire sidewall of the tube as well as the corners. I repeated this three more times to complete the first tube. I did four "pours" for each frame tube (one down each wall) and let each tube drain into a tunafish can for about a half hour (reusing the drained oil for the next tube).
I still need to do the three welded crossmembers (which have no access to the ends of the tubes). My plan is to squirt oil into the holes and rotate the frame in hopes of covering most of the interior surfaces, especially the welds at the ends.