I wrote an article for the model ship mag Ships in Scale a couple of years ago on building a spray booth. Unfortunately, I cannot find my copy of the article to give you issue number.
I built the case out of particle board, and used a 14 x 20 furnace filter for the filter. I used a muffin fan for the fan, and built a light into the top of the box. I'll keep looking to see if I can reference the issue, or else rough out a sketch of the arrangement.