If you have things apart to grease the slider pins etc, I always give the rotors a scotchbrite treatment. Not needed, but makes me and the trailer feel better
Something I have been doing for years now is after washing off the trailer (after a dunk in the chuck) is liberally spraying the whole brake /wheel assembly with Fluid Film. It doesn’t seem to cause any issues with the pads and seems to keep everything corrosion free... just my 2 cents. Napa has Fluid Film on special from time to time and I buy a case when on sale.