I hope this isn't too blatantly "self-promotion"-ey, but because you specifically mentioned James Nestor, I thought I would put this here:
I made an app called One Deep Breath that features many of the breathing patterns and techniques described in the book. Nestor has been a huge inspiration for me.
It is available for early access on Android and iOS.
Try it out and let me know what you think! I have received awesome feedback from this sub in the past, and love it when passionate breathers try it out!
I can also really really recommend this book: https://www.amazon.de/Coherent-Breathing-Aligning-Breath-Heart/dp/3960515383?ref_=d6k_applink_bb_dls&dplnkId=d5aaf474-122a-4559-b583-39f3056ce6e1
1.25 cm does the job vertically across lips, £7.50 for 24 x9 meters: Micropore Surgical Tape White 1.25cm x 9.1m (Box of 24)
https://play.google.com/store/apps/details?id=com.abdula.pranabreath
I tried 30 application and this one is easily the best one. Lots of breathing exercise that you can modify, create your own, view you stats for day, week, months
11/10
I recommend starting with Nestors simple slow breathing technique, which is a 5.5 second inhale followed by a 5.5 second exhale. This is the "Optimal Everyday" pattern on the app.
Do this for a minute a day. Then work yourself up to 3, then to 5, etc.
What you'll find is that over time you'll begin to breathe slower and less.
There are tons of really cool techniques out there that you can use, but for just starting out I think that this pattern is one of the most effective.
Also, try this link out on an Android device?
https://play.google.com/store/apps/details?id=com.zazen.onedeepbreathalarm