I gotta pull you on that one, a circular saw with a guide ( i welded myself a t shape about 700mm long that fits in my saw guide holes ) is way quicker and more accurate. Its square all the way, no wander.yes to hand saw or big knife. Cut slightly oversize so it's a tight fit.
Power saw really bad with dust everywhere, and no faster.
A table saw is even quicker again. I have a dw745 with site extractor ( yes, still some dust gets thrown about ) but its so fast and repeatable. If you are cutting over 70mm, you flip the sheet and run again, perfect cut.... i usually aim for 1mm under and its always a tight fit