Notorious explained valve adjustment well.
I would add, watching the valves as you turn the engine to adjust the next pair in firing order is OK, but, on an 8 Cylinder that would be 1/4 turn, on an inline 6 it would be 1/3 turn, and a 4 Cylinder 1/2 turn.
I confirm the timing mark on balancer is correct then put a dot on it straight across from the tdc mark then half way between those and you have four evenly spaced reference points. A little bit off will not matter because of the lifters being on the heal of cam when you set them.
Turn engine two times and you are done.
I could get into push rod length and a lot of info on valve train but another time.