+1 on the Oxiclean. I usually mix up a little over 3gal of Oxiclean solution in my BB, put on a carboy cap and suspend it upside down (I found a large stock pot that supports it pretty well). Let it sit overnight and flip it right-side-up for another ~12 hours. The carboy cap does a good job holding the solution in, and if you use warm water, you'll get negative pressure inside the BB as it cools off, which keeps the cap solidly in place (I usually open the spigot after an hour or so to keep the carboy from sucking in too much). With >3gal, the solution will cover every bit of the interior surfaces after the carboy has been upside down and right-side-up for some length of time. Also, the toughest spots are usually at the top of the carboy, which is why I flip it upside down first (while the solution is still nice and hot). Every few batches I'll take the spigot apart and soak all the pieces. Also, I occasionally switch over to PBW just to make sure I don't end up with an Oxiclean-resistant bug.