I've been sprayed with OC spray as part of a course. The spray was about 1/8th of a second blast in my face. I was allowed to hold my breath and close my eyes. It's a delayed reaction, meaning that it wouldn't IMMEDIATELY stop a threat... however, after about 5 seconds or so, the searing pain was nearly incapacitating. I was allowed to towel off the excess OC spray. I was forced to do 'react to contact' drills under paintball fire, and I will frankly and honestly say that I could barely function. The searing heat and pain lasted hours, and gradually got better over the course of 10 hours and it was finally gone after I showered.
The brand is Fox labs. I have no affiliation with the company, but afterward I ordered several cans of it.
That being said, I would only use it if I were law enforcement trying to detain someone, of if there was a threat (for instance and unreasonable person I know gets too drunk, maybe a family member, and starts a fight, or maybe a dog fight, etc.). For most self defense if there's a violent person with a weapon I'm using my gun for defense. OC Spray is not generally in my self defense continium unless I am someplace that I cannot have a gun.