I was the same way. Up until a couple weeks ago I would also get around a 6/15. I never really liked the rapid glance technique, but now I use it and just trust my gut. When things get tough, I'll cover the two angles with my thumb down to the vertex and see which is better with rapid glance. Give it a shot. I haven't missed a single angle question on full length test 1,2, or 3 using these methods. Haven't done laptop or hill for any of these tests, only the methods I just told you. Other than that, I just say practice practice practice.