"spinning the pushrod is almost guaranteed to make things too tight."

I have always used the spin method. I spin it back and forth in between my fingers and when I feel it start to resist, I tighten 1/2 turn more. Now I am worried it is too tight?

 

You are fine.

 

Gracias. Is there some method of using a dial indicator to determine this?

 

Yes, you could use a dial indicator to detect up/down movement, but it would be way overkill, IMHO. The nice thing about hydraulic lifters is that they can handle a wide range of preload. Minor changes in preload can be made to suit your needs. As long as you are consistent from one to the next, you should be fine.