I... uh, how do I say this... stroke the pushrod up and down like I was.... uh, you know, practicing for something.
When its loose you'll feel the pushrod go up and down. As you reach zero lash it won't anymore. Don't use spinning as your guide. Your low-duration flat tappet cam has very light springs, and you could probably spin those pushrods at full lift if you wanted, so its not a good indicator.