Cheap, Quick, Easy...
Successful experience... BRUSH if you're not wanting to spray.
If you must paint it in place, my best advise is to use an off the shelf alkyd epoxy tub and tile paint kit. Go through the back door of a body shop and pay the painter to tint it for you if the common bisque/almond/white doesn't suit. Clean, #220 scuff, clean, tack-rag, tape, tack-rag. If you open the windows and ventilate with fan, you'll get dirt in the coating. Keep trailer closed, wear a real respirator for a clean surface*. Follow exactly the directions on package including temperature. It takes two coats. Yes, the mixed paint/catalyst will keep perfectly well in the freezer overnight for the second coat. If you're not familiar with brush painting protocols, read up on brush painting. For even coating, it is very, very important to use the Purdy brush pictured. Work as fast as reasonable 'til finished, then wait. In a few hours, the paint will flow out and look like porcelain. You will not have to color-sand the orange-peel left by a roller. Roller is bad, unless you prefer orange-peel texture.. It defies logic that the hemispherical sink in the video can be evenly coated with a roller, perhaps a "wonder of television". If you do get a sag, don't fret, wait a few months, and color-sand.
I had no need to color-sand. If you can find a run, brush mark, or sag in my brush job, I'll sign my title over to you.
*Advice from the “G-String” Painter... When painting with body over an object, take your shirt off, rub yourself down with lotion including your hair, wash your hands well, don't touch the surface with anything but the paint. Most of the junk that falls into your paint, is clothing fibers, dander, hair, lunch...