It's a catch 22 sort of situation, but think of it this way. If you do that to 5 girls, hang in on the convo for around 2mins each at least, then all the other people will see you having spent the first 10-15 mins in the club, talking to a shit load of bitches.

Your are now that awesome guy who seems to know a load of girls. Then you'll feel good about yourself as you'll have made a few girls laugh, got on good name terms. Also now you know that if you have another quite peroid soon, you can go back and talk to some of those earlier girls again.

Never stand alone at the bar (or anywhere) as it just looks creepy. Heck even if you talk to the bouncers/bar staff for a bit, get on their good side so that in future you feel like you own the club.