I worked on the big brown trucks for 15 years, and all we did is crack the bleeder on each wheel 1 at a time and keep the m/c full, and run until clear. Unless the system is empty, you should never need a power bleeder, gravity works just fine. To make it a little less mess, take 3 foot of 3/16 id vac hose and push it over the bleeder and run into a jug or pan with floor dry. This will not take 20 minutes. If you feel the need to spend $50 on a bleeder, just send me the $$ and I will send the 3' hose.