The Stovebolt Site Forums The Parking Lot Big Bolts Bleeding a Bendix Hydrovac equipped brake system.

http://precisionrebuilders.com/hydrovac.html

From that page:

Install Booster
• Connect all lines making sure all fittings are clean.
• Bleed hydraulic system using a pressure bleeder.
• Do not run engine while bleeding hydraulic system. (See "Bleeding Procedures")

http://precisionrebuilders.com/ts_hydraulictrbl.html
Bleeding Procedures

I know very little about the Hydrovac, but I think I adjusted mine with the engine off (54/55 2-ton GMC).