How does trons "measure the chainline?"

I have a steel 15" ruler and I lay it across the flats on the chainring and look to see how it lines up with the cog.
This method doesn't work very well because, apparently, I don't have a very straight or flat chainring.
So, I average it out and make an adjustment, and put everything back together.
Then I spin the crank and wheel and look and listen, and look some more.
Then I take it all apart and make another adjustment.
It takes me about an hour to adjust my cups for proper tightness and chainline.

When I got my Phil crank bearing my lbs told me to get two cup tools, and I did.
My lbs told me right.
Having two cup tools makes it much easier to do everything, but mostly to guage the tightness by feel.

My cups periodically loosen.
I know I could put locktite on the threads and they would stop loosening, but I need to learn more about tuning my crank bearing, so I will do it a few more times before I locktite it.

I can't tell from looking whether or not I have a straight chainline; but I have a dead silent chain and so I feel in the ballpark.
Park used to make a chainline tool, a CLG-2 Chainline Guage, but they have discontinued it.
I should try to find one before they all disappear.