sorting sreface rust on chassis?

[Bonzo]

I guess the easiest way to keep the rust at bay is to keep the bare metal well oiled until you are ready to paint the chassis, a nice oily rag should do the trick.

Best not to work any oil into unwelded joints though

Duck oil works quite well, this tends to leave a nice light coating once it has evaporated & will burn away quickly if the area needs welding.