Like most second-hand work vans, it is very likely you are going to have to deal with a little bit of rust. Quite often the rust will be easily visible, but sometimes it is not as easy to spot as you may think. One thing to look out for is bubbles forming under the paintwork, like this:
If you find your some bubbling like this, you can be sure there is a little bit of sneaky rust hiding underneath. From our experience the rust had spread further than the actual bubbles itself, usually by around 2-3mm. To deal with this we used some sandpaper or a steel brush to remove the paintwork and the rust, and we kept going until all the rust was gone and we had a nice, smooth surface.
Once the rust was gone we applied Brunox Epoxy to act as the rust neutralizer and primer, and after giving it 1-2 days to dry, two layers of Hammerite Direct to Rust silver paint. The drying time for the Brunox and the paint of course varies based on the temperature outside. We did this in the middle of a Swedish winter (albeit an abnormally warm one), so we gave it a little longer than usual. Before applying the paint you should thoroughly clean the surface, ideally with isopropyl alcohol or similar.
For the tools we used a mix of sandpaper, steel brush, an abrasive sanding block and some rags to wipe down the surface. Most of the rust we cleared was outside the van, however we did clean a few spots here and there within the cargo hold.