Hey,
I would say don't use tin foil, just get some posterboard that's a flat white, tape that stuff on the sides and you're good. put some type of tray to collect run-off water at the bottom under your pots, which should have good drainage holes. I would suggest adding a 30% perlite to your soil mix to aid in drainage. Follow the instructions that shows you how to build one of those grow-boxes. I have seen that setup work quite well. just have to get it all dialed in correctly.
Hope some of this helps. :]