Been to a number of gloryholes and always had a good time. Cleanliness can be an issue so always trust your best instinks.
I like the ones that have multiple holes as they accomdate a larger number of participants. Also the ones that have handles placed above so the receiver can hold on to the wall are nice. And at times I just like to watch the guy jerk so multiple, larger holes are nice. Plus it works both ways if you like being watched. I do not ever recall seeing a women in one but plenty of guys in panties, dresses, nylons which can be hot.