What about covering everything in Panada Plastic (black white plastic). it would give you a scrubbable surface and then you wouldn't have to paint styrofoam etc. It's real cheap too, hence easy to replce each grow if you wanted to.

I think you have the scubber in the wrong place. Someone will have to validate this for me. I think it has to go on the "suck" end and you will be sucking air out of the room "blowing" it outside. Check out user spaceneedle as there is some excellent venting information in some of his posts.

Good luck.