help rocker ajustment

doesn't that get messy? and how are you turning the adjuster and lock nut accurately when it is moving up and down like that? I remember my old shop teacher in high school telling us to do it running, that just seamed weird to me, more trouble than its worth, I have never done it running and never had issues

When I adjust rockers while running I set a piece of cardboard about 6 inches wide and as long as the head down between the valve cover rail and valve springs to keep the splattering oil from goin everywhere.
I'ts a little hard on feeler guages doing it running, and you have to use a loose grip on the locknut and adjuster wrenches so they can move up and down while turning them.
Kind of just have to let them float around in your hand.