In my life, I've been on both sides of the gloryhole.
Oh? What's on the other side of a glory hole?
Depends on the girl you meet, but it's fun.
You can do whatever you want with what's provided, but that is a risky thing to want to do. You need to have more care than that, because  you don't know what's on the other side of that hole, and you don't want to be at risk for diseases.
You're exaggerating. I'm not risking anything.
In most cases, it might be safe enough, but there is still a chance you could be having a sexual encounter with someone who has an STD or a wish to harm you. It's better to practice safe sex.