Best white paint

The "best paint" is defined by the job at hand. Auto finishes are considered to be very durable and are used by spraying in a lot of applications. You don't need that level of paint to paint aluminum siding, though. There are other quality paints that are easier to apply and results will be good.

I'll post a few pictures of the process of painting my old Starcraft for you. FWIW, I paint some stuff for a living, mostly residential and commercial structures but have experience with vehicles, tanks, cooling towers, marine tankers, etc.

The paint I used on my RV trailer all came from Sherwin-Williams. The process was this: fill holes and small dents with filler, clean all surfaces with a phosphorus based cleaner like TSP. I used Jasco, sold at big box stores and is easy to apply. Spray cleaner on surfaces with garden tank sprayer. The cleaner removes any oxidation in the surface and removes enough gloss from the painted aluminum to get a good bond. I primed the whole siding since I used an airless paint sprayer and masking off and painting was a small part of the process. I used Sherwin Williams Industrial DTM primer, an excellent product and bonds good with bare aluminum or pre-painted surfaces. The finish coat was Sherwin Williams Super paint, a latex based house paint and I've had good success with it in a variety of applications. The whole application of the main body was done in a couple of hours as I was trying to beat an incoming storm. Later, I spray can bombed some accent stripes since it's easier to apply that in small areas and offered a good finish. IIRC, I used some type of Krylon.

Here's the images:
Original masked:


Primed:




Finished:






Since the paint job on the siding, I have painted the bumper, my sewer hose, holder, the tongue, and the box on the tongue with black. The storage cover on the back and the main door are now both the same body color (I didn't like the white). The roof got a couple of coats of white acrylic roof paint. All of the paints bonded well and a scratch revealed that the primer is sealing the siding.

Good luck on the painting. You could roll and brush these paints but using an airless sprayer and masking is faster and better results. You can rent a sprayer for a half or full day from Sherwin Williams or a rental yard. It is inexpensive.

Boat painters (who don't spray) usually use the roll-and-tip method. A roller is used to apply the paint evenly, and then you go over it with a high-quality fine-bristle brush. The paint flows together and produces a good finish.

Is the current finish just worn and faded, or are there are spots on the aluminum?

If you are just painting over the existing paint it will be easier.

If there are spots down to the bare aluminum, those have to be handled carefully. Aluminum oxidizes very quickly, so you need to prime the spots right away after light sanding. The best primer for aluminum is zinc chromate (yellow-green color). You may have to go to a body shop supplier to get zinc chromate because of its toxicity.

Steve

I agree. You could likely go anywhere else and get more help. Not that that's a good thing. Try using the search terms: best white paint aluminum trailer. I used a Safari browser and there appears to be lots of information out there. I also looked at the 'Images' tab. There are photos of trailers people that have restored - you might check out those websites too. old trailer.com has a Resources link that lists many forums for those that have restored trailers - hopefully you can find information there. Good luck!

Why not ask at a body shop ?

Don't have the answer but I would have searched the internet for it where there is a much wider audience than this forum.