I use an old Harbor Freight compressed air venturi to suck a vacuum on my extraction bottle. I use a 1/4" ID air hose to slip on only brass hose barb. Fast and cheap. A rubber tipped air blow nozzle lets me pressurize for dispensing via the same brass fitting. The real Topsider has a piston and is hand pumped for vacuum or pressure. They seem to be nice units that people review well, but I'm cheap and had an old 3 gallon propane bottle without the float valve so couldn't be used anymore.
Draining doesn't get all the oil out either, by a long shot, so I don't worry about flushing. In the Listeroid I remove the large door to change the cotton rags in my gravity-bypass filter, (aka "sock in a box") with every oil change, so am able to suck it down to the last drop by the drain plug through the large access door and then usually wipe out the sump as well. For all other equipment, I just suck it down to the bottom of the sump, including my MB 300D.