Various suggestions about polishing, so I will comment on the water drops. If you don't already have a synthetic chamois type of drying cloth. It absorbs water quickly. It is night time otherwise I would look at the brand name for reference. Don't wash your trailer when the sun is is blazing hot, and wait until your trailer is either shaded, or early morning, or early evening. If you choose to wash with a little sun, just do things quickly before the water drops gets a chance to dry on the surface.

I use an electric garden blower to dry my trailer after washing. It drys quickly, gets the moisture out of the crevices, and minimizes rubbing a polished trailer using drying towels. Once most of the water drops have been blown off, I use the synthetic towel to lightly and quickly pick up any moisture still left on the trailer.