Hmmm... vandi, sorry to butt in, but did you read the manual. The reason I'm asking is that you might not have to go out and spend $40 on a remote shutter. I don't know about the rebel, but the 5D allows you to have a self-timer in bulb mode. Basically you set the dial to Bulb, and then the self timer. The timer runs out, and the mirror lifts and holds until you press the shutter again. Some may say this will induce shake. I seriously don't think that they understand how this whole thing works. First off you want to capture for 20 minutes (what purpose this may serve, the world may never know). A couple of seconds will not effect your shot, as it's averaged.
This is the basis of ChisA's suggestion. You are exposing something for 20 minutes- unless it's a black hole, you'll get a nice white frame (you might as well shoot a white wall at f/22 and out of focus). By reducing the amount of light that is averaged out by a factor of 2, you might actually get the effects you're seeking and not blow out your chip. Using the hat trick WILL NOT damage your equipment. Anyone that suggest that, is simply misunderstanding the concept of it.