Angle torque is performed after a preliminary torquing has been completed. Generally the fasteners are a stretch type and a one time use only. The method I use, I'm sure there are others, mark each fastener with a paint pen and then with my big breaker bar I make note of my starting point and crank say 90 degrees. 360 degrees is one full rotation so 90 would be a quarter turn. I use the breaker bar swing as one gauge and the pen marking for verification.
Rob