I use the grid, speed of greens and instinct to putt. I always use a cross point on the grid for breaking putts. Use your gut and you will find a cross point that you know will not work above the hole. You can then find a cross point that you know will not work below the hole. Take a little risk and use the middle one as a starting point. I also use the reverse view to see the break at the hole, this may cause me to "rethink" the point i will use. I also like to aim at the top of the hole so the ball will fall into the hole on a minor "miss" of the dinger. Green speed familiarity is critical to using the grid too. I may be wrong, but I have found the green speed to be as follows(especially up to 30ft meter) ;
Slow 6 ft per putter movement
Normal 6.5 ft per putter movement
Fast 7ft per putter movement
Very Fast 7.5 ft per putter movement
Tournament 8 ft per putter movement
Try this and i am sure you will have less 3 putts.
Wild Bill