Hey mate, i wouldnt sand blast it imo. We did a trailer at work then painted it and had no end of problems with valves going tits up. Ended up changing every valve on the trailer just to get the brakes and extender to work again.

So when we did our big daf we stripped it down and used a needle gun, took longer but was a better soloution in the end.

Jsut a bit of advice as it turned out to be a fuckin expensive spray on the trailer