in my spare time i restore old vw's, ive had plenty of body shells/parts sand blasted in the past, Usually by the guy who will be painting, albeit in spray or powder.
If ive had stuff blasted on site, i try to get it covered in paint with in 4 hours ( summer time ), in winter you are fighting a loosing battle.
Best thing to do is, give it a flash over with some primer, ( primer is porous and will still rust through eventually ). but it will slow the dreaded rust worm..
I would try to avoid covering it in any oil based products, unless you intend to keep it bare.
But as one on here said, sand blasting will get rid of every thing..
Powder coating in most cases is kind to the environment, and will last longer.
Hope ive been help full