I have had a couple of syringe type extractors - but although they work with EP 90 well enough the Draper one couldn't suck DIII (the Sealey one was fine). Point being, you may find that pumps suited to oil might not work for ATF - though the fuel syphon idea is probably spot on. But with EAS at high, and a pail underneath it takes seconds to undo the drain plug, and a few minutes to drain (drain a warm box) - sucking it out manually would be a right ball ache and wouldn't improve the recovery, and it could be tricky to measure the volume removed, too.
As also mentioned above - be sure you have the right level to start with, and then measure what you remove. I would add back the same less 1/2 litre, and then take the level (cold and running, all gears etc) before adding the remainder. The dipstick tube is near horizontal as it goes into the filling plug and takes v little volume to go from Low to High - if you go over then you either have to tap some off/ or suck some out