I'm not a pepper spray teacher either, but I've also heard that Sabre Red is good. I've also heard good things about Fox Lab and Defense Technology. I didn't know about POM, but a cursory glance suggests its appearance is meant for non-permissive environments. By contrast, a certain commonly found brand doesn't have a very good reputation, so anyone who is looking for brand advice should do a bit of research.

It's hard to find pepper spray training, and with so many people carrying spray, there is really a need.

As for size, currently I have 1.5" diameter canisters. It's ergonomic, but noticeable in the pocket -- even more so than a pocket gun holster because of the shape. I am thinking of going down to 1" to it'd draw less attention.