[Bwana]

I just recently did this procedure. I took out my taillights (look in locker for a cool picture). Took out the bulbs, then setup a travel hair-drier my mom had (smaller nozzle output) and put it in the hole for a while. Overnight i set up all the lights in front of a box fan, and let them sit there for overnight and the next day. When i put them back in i put a bead of silicone around the outside of the side ones. It looks like water running off the back goes right over the seam, therefore letting water seep in. So far it's been 2 weeks and no moisture has returned.

I would recommend against drilling a hole, my logic being that it is easier access for water to get back in, in the form of humidity. Only use the hole method as a last resort.