You'll see several threads on this topic on R.A.S. There's definitely a "reward curve" as far as how much effort and cost you really want to put into an aluminum tube trailer. I'd argue that it only needs about a 10 foot refinish (i.e. looks good from about 10 feet). In that case, using an aluminum boat refinishing process can get the job done for less than $500K in materials (self-etching primer and a rolled-on topcoat). We've had several jobs done at our field using this sort of process, and they really do look good. One of the nicest is an Eberle trailer (fiberglass but same general idea) that used rolled-on epoxy-based paint. Looks much better than factory original and has held up for 10+ years.