When you get to the part of the build that requires brake bleed, this trick is free and no expensive specialty tools are needed to vacuum the freshly laid lines. Here is a vid I made using a shop vac. Rear brakes took a lot longer but they will eventually bleed. I have an adjustable brake bias installed in the rear and I have it turned clockwise all the way to the right. All brakes bled on less than a 32 oz bottle.
https://youtu.be/CGv_SWuoxT4