Some people have asked for pictures of my spray booth that uses a shop vac. Here's how I made it:
1- use 1x6 pine to make a box which fits a 25"x25" furnace filter. This also has a 1x2 frame inside of the box to keep the filter flush with the front. Use a piece of particleboard on the back and seal it to prevent air from coming thru the back of the box.
2. Cut a hole in the side to fit the vacuum hose from the shop vac.
3. The exhaust hose is attached to a 90 degree elbow and a shower drain that fits thru a piece of plywood. The plywood is cut to fit the window opening. This provides a sealed system that uses the shop vac to draw the overspray into the furnace filter and exhausts the fumes outside.