This is a tip - Kind of - more opinion. My opinion is that shave brush performance is best if not splayed more than 25%. I don’t have facts, but some anecdotal info; which comes from badger brushes. Those soft badger tips are fragile. If you purchase a badger brush from Simpsons or Thater it comes w/ directions talking about how fragile the tips are. The specifically say not to use the brush in circular motions. Splaying a badger brush and going in circular motions will cause the stalks of the badgers to break if done over time, leaving a hole in the middle of the knot.
I’m comfortable with what I’ve said thus far, now it’s time for opinion. I like synthetics. I have nice badgers, though reach for nice synthetics. The nice synthetics I’m familiar with are meant to copy various aspects of quality badger brushes. I’m making the assumption that based on that, the synthetics are designed to be used like badgers. I’m really pleased with the performance I get by not splaying.
I don’t like to refer to ‘right ways’ or ‘wrong ways’ with shaving because there are many variables and different approaches work equally well for folks. Also, I haven’t shaved half my face with a splayed brush and the other half with an un-splayed brush, which I believe to be the acid test of drawing conclusions.
Thanks for reading!!!