Russell makes spring loaded bleeder valves that they describe as a one man brake bleeder. They are nice when it comes to stopping air from creeping back through the valves while bleeding. When used with a Mitty power bleeder, they work very well.

One of the problems with the factory style bleeder, is that air can seep past the threads while the valves are open for bleeding. I wrap several layers of Teflon tape on the bleeder threads to counter that air intrusion. It seems to be effective, as well.

A proportioning valve is a band-aid for improperly matched front and rear brakes. Caliper bore size, number of caliper bores and correct matching of front and rear caliper bores, plus the correct master cylinder sizing is critical to get the brakes properly biased. The clamping force of the front and rear calipers should be properly matched so they provide the proper level of front to rear bias without the need for a pressure reducing or proportioning valve to try and fix a mis-matched set of calipers.

Another brake system item that many are unfamiliar with is a hydraulic pressure shock reducer that cuts down the pressure spike of the fluid to the rear brakes and dramatically reduces rear wheel lock-up when the brake pedal is applied suddenly at speed. It doesn't reduce the line pressure, rather it just dampens the initial shock wave during high speed, spirited brake applications. It's well known on the racing circuit, but seldom mentioned hear.