I am surprised to learn here of the need to purge oil with even modern aero engines, the Rotax; is that right?
The oil dipstick on the Rotax 912 of the Flysynthesis Storch and Texan our club has can be read without 'burping' the engine.
its not mandatory to pull a rotax through, and it also depends on the installation, as its a dry sump setup, the location of the sump in relation to the crankcase will determine if you need to pull it through to get an accurate oil level on the stick, if the sump is high, the oil will drain back to the engine, and need a pull through to get it back into the tank, if its below, then its not needed.
i dont mind the need to burp the oil, it does a few jobs, first, you now have oil pumped through the engine before its started, you get an accurate oil level on the stick, and you can feel the compression on each cylinder as you turn the engine over. not only that, the external oil tank does a great job at cooling it also.
i am also aware of the treat every prop as live mantra, so myself, and i teach my students when pulling a prop through to burp the oil, stand behind the prop, and pull the blade down from the top to chest height, so if the highly improbable happens, and the engine starts, the aircraft will move away from you, and not through you, the wash will push you away from it, and the wing hitting your back/or lift strut in a high wing will also hopefully stop the aircraft from racing off any thurther.