Like you, I've read all I could find. I don't think there is a sure fire mechanical / mathematical method. Just like RL golf, faster the green = more break. Harder hit the putt = less break. Uphill takes less break. downhill = more.
If there was a way to measure the speed of each "grid", and they behaved like wind effect, I suppose you could work out the various breaks depending on putt speed. But I went with a more standard approach:
Play practice rounds and when you get to a green forget the hole. Pick spots on the green with breaks and putt to them. Putt back and forth to two points and see how the ball rolls and the effect of slightly less and slightly more speed on the stroke. When the shots run out, rinse and repeat on the next hole.
If there are certain holes on certain courses that you end up with similiar huge breaking putts, do the above. But this time, putt around the green looking for area's where the approach to the hole isn't so diabolical. Note it, and hit to it next time you play ignoring the pin. Either that, or keep practicing the putts until you "get the break".
Best I can offer mate.