I hate rust too but my solution was a bit more simple
I had a coffee jar with an oily rag init every time i finshed a section out came the rag and wiped over the rellavent chassis parts with oil
to stop the condensation from my aluminium roof dripping on my chassis i put a membrane stretched across the roof joists above my build area
this worked well and kept my chassis rust free for nearly a year before i painted it obviously you need to degrease before painting
Ray
