I use the clear tube and the reservoir from my Mitivac to catch the fluid I bleed out. That reservoir holds 1/2 cup, which ends up being the perfect amount for the van. Every time that reservoir gets full, I know it's time to add more fluid to the van reservoir. Due to the fact brake fluid absorbs water, whenever I bleed, I also flush. I flush the system simply by doing an excessive bleed. I like to get at least a half cup of fluid from each bleed point on the van. If the fluid looks dirty, I keep going until it gets clean. As BB points out, flushing periodically and keeping the fluid clean protects the system from pitting and other issues. Tim