I bought my 8.5x20 used floor had stains all over it. i went to lowes bought a deck cleaner i pressure washed the trailer from roof to floor and everything in between as i went i used a deck brush and cleaner and scrubbed everything down. let it dry out for a few days then i primed the roof & walls and 2 coats paint. then i put a coat of floor coating down on the floor and 12 inches up on the sides (i put a kick plate all the way around with 3/4" plywood to prevent damage to the walls) next second coat on the floor this time as i went i would do a small section then sprinkle sand on it then re-roll the area and worked my way out. the sand provided a non-slip texture to it. I am extremely happy with how it turned out here is what i used.
Primer- white - http://www.coronadopaint.com/viewProd.asp?prodID=3
Paint - beacon gray - http://www.coronadopaint.com/viewProd.asp?prodID=28
Floor coating - battle ship gray - http://www.coronadopaint.com/viewProd.asp?prodID=43
i got the paint from my local dealer they sell benjamin moore paint to home owners and if a special request but the coronado is what the painters use unless a customer has a special request on brand i use the coronado for everything. good luck