That's a good idea; carrying the leash out with you.
I don't know the exact reason, but dogs will do exactly what you describe with the ball in their mouths.
Perhaps, instead of a squirt bottle, you could try air?
I have a squirt bottle, too, but also 'canned air' meant for dogs, because the squirt bottle isn't always handy, you're right. There are small cans for carrying in a pocket.
All they are is noise, which the dogs hate. You don't point it at them, you just push the button to make the sound. Eventually, though, they catch on, and all they need to do is see the can. If you are ever interested, I can give you a link to the one that I have.
Yep, Boy and my Ds.
As for Dgs, you sound like me. Knock it off would have been my response, too. I don't want anyone teasing my dogs. :-(
Love All Life, Thank You For Posting! :)