ok you want to feel a little drag on the feeler guage as you slide it in and out constantly as you tighten it.

Basically you will wiggle it in and out between the rocker and the cam over and over again until you start to feel a little drag. You dont want so much drag that it hangs up, but just enough that there is some resistance when moving it in and out.

Then while adjusting it keep the feeler moving in there. To make sure you dont move it while locking it down.

Let me know if this is helpful or not.