Ok heres my input, I resined the front of my box for a lil extra strenth and the rest just left alone n primered, when I painted it i noticed that the resined front the paint stuck alot better, especially the edges, the edges on the untreated MDF i had to put 6 or 7 coats of primer just to get all the wood color to go away, and still paint wouldnt stick, especially white, it would litterally soak it up as soon as i sprayed it on there, so i would say, put a nice even coat of resin over the entirety of the box, sand all of the rough edges, bumps, etc.. down with a heavier grit then resand with a fine grit to keep it smooth, shoot it wth a coat or 2 of primer, sand, paint, n 2 layers of clear.