I already told them weapons would be better than spray but that's not what they want so I'm not looking for "tell them to carry a gun" answers LoL

I know nothing about the stuff. I figure some of it is better suited to be sprayed on tacos than a booger's face. and some will send a large crowd crying to mommy with a single spray.

Are there ratings for their strength?
Whats the shelf life?
What are some preferred brands?
Things to consider when purchasing?
Do they make trainers?

The girls jog a bit and want something to carry while on the run, literally.

I did some amazon searching and theres some with a "joggers strap". Some are cheap, some pricey. Id figure they'd need a couple cans....? One for car, one for purse, one for jogging, maybe even one for the desk at work?

school me! - and them lol

Fox Labs 5.3.

Amazon

Even though I carry a 9mm Shield, I still keep this Fox Labs in an outside pocket on my purse. It came highly recommended by multiple Arfcommers.

You can read more about the specs on the manufacture's website.

Stress to the GF's friends that they have to have the pepper spray out and in their hand for it to do any good. And they shouldn't be running with earbuds in.

Another option other than a gun that they may be more comfortable with is recommending that they carry some sort of pocket knife in addition to the spray. That way they at least have the ability to defend themselves with something other than a can.
(This is what I convinced my sister to do)

Learn some hand to hand skills.

I work in a prison as a Corrections Officer.  I have encountered a few prisoners who are pretty much immune to the effects of pepper spray.

Any idea if that is from repeated exposure, or just good genes?