That is the method I've used for years on race cams using the starter motor at the races or with the car in the shop
On smaller street and strip cams you can adjust both rocker arms with the piston at top dead center on the firing stroke starting with cylinder #1 and then follow the firing order to adjust #8 and so on which means you do get to adjust all eight cylinders valves with one and 3/4 revolutions of the crankshaft