You have to remember what Bonnie's style is - scrappy - and combine that with her "scrap user's system." For the most part, she's not cutting strips when she's making a quilt. She's already got those strips cut, having them cut into the most commonly used sizes.
Thus, she's got lots of strips (2 and 2-1/2") that, using the Easy Angle, give the size hst's she often uses. It isn't the ONLY method she uses - she's also got a link on her website for a free printed sheet of hst's. Inklingo, maybe?
I've done lots of her quilts, and sometimes use the EA, sometimes not, depending on what I'm cutting from. I will say that, having the strips right sides together, cutting carefully, sewing carefully, you'll get a perfect hst. Do a few first, to make sure you are using it properly. Also check that 1/4" seam... They are often off just a smidge. Someplace in her tutorials or on her blog, she addresses how to check that and adjust if necessary.
Personally, I don't know of any other designer who does so much for free! You could easily spend hours on her website - then a few more on her blog, which will lead you to her quiltcam (or archives of them that have recently started being put on Youtube)... You get the idea, lol.
http://quiltville.blogspot.com/p/videos.html