I recall ages ago shown ages ago a method using your hand. I am not sure if is is the same as the thumb method.
Using left hand for left turns, and right hand for right turns. Hold index and middle finger as is "V" for victory. The thumb was extended out and down. Place the index finger at the on your current heading. If the holding radial was in between the "V", then a teardrop entry. If between the index finger and thumb, then a parallel entry. Anywhere else, a direct entry.
I have memories of it being effective.