The opening of the booth is 40" wide x 29 1/2" high. There is a fan installed in a 12" dia. exhaust. The booth uses regular furnace filters (removed before taking photos).
If this is what you have, does the paperwork mention the fan rating (CFM)? Also I wonder what the manufacturer has suggested in terms of drainage. What was YOUR approach to it, and how do you like the result?
As you can see, the bottom is flat. I have a few ideas ranging from using old newspapers to collect the moisture to drilling a hole in a back corner and slightly tilting the booth so that water flows toward the drain. A properly shaped secondary floor with a drain is something else that comes to my mind. Rails directing water toward a drain location is yet another idea (the easiest would be to have it drained over the front edge, but it sounds almost as ugly of a design as using newspapers).
Any ideas are welcome.