It sounds like you're trying too hard.
But it is a tough thing to do successfully. I guess how I do it goes like this: The first time you run a nymph through a given run, pay attention to what the indicator does. Your fly should be ticking the bottom occasionally, and this should be shown by your indicator as well. Ideally this will look like intermittent pauses where the indicator isn't moving as fast as the surface water itself. If a pause looks too long or somehow different, set the hook.
If the indicator goes under- set the hook. If the indicator goes sideways- set the hook. (sideways is the movement most correlated with a take)
Its tough, and takes some practice, but make sure to have some fun with it. When I 'm fishing nymphs, I bet I set the hook 30+ times per hook-up, but its still my most productive method of fishing.
Also, Palsa's can be a bit tough to see since there's just not that much floatation there. I like the foam football shaped ones about the size of a cough drop for rough water. like deez-
I stick with white, cuz bubbles are that color. If you see chartruese or chernobyl orange bubbles, I recommend evacuating the stream immediately.