Here's a link to how I cut bias binding:
https://drive.google.com/file/d/1Iq4...zIRerXHp8/view It's the handout that I give my students when I teach the Beginning Binding class. We fold the fabric, cut the strips with a rotary cutter, then sew the ends together.
I did the triangle method you're talking about ...once. That is pretty time consuming! ...drawing all those lines and cutting with scissors.