As you're walking from your car to where ever it is you are going... Find a group of like 2-3 girls.

Say "Hey, I'm not from around here... I wanted to check this place out. Is it cool if I tag along with you guys until we get inside? I'll buy you your first round of drinks for being nice!"

You're seen walking into the bar and at the bar with 2-3 girls.

Simple.

Most clubs are pretty empty when they first open at the start of the evening, that's the best time to go in and get chatting with the bar staff, do this 2 or more times a week over the course of a month and before you know it they'll all know you! Then you have instant social proof whenever you go there and it makes approaching at the bar 10times easier because barmen are usually pretty socially savvy and will wing you if you are cool with them.

How to avoid actually buying them drinks once inside though? Just ditch them?

You could ditch them I guess.

I usually just buy the girls drinks. No reason to back down on a promise and be a cheap ass. Plus, you're seen at the bar by everyone having shots with 3 girls. And you're asking for social proof?

It's a good way to establish social proof but I thought you never want to buy women shots (in general).

I don't see why you can't just open girls on the street and be such a cool guy they want you to come with them, you should never have to bribe them with drinks to 'let' you come with them. It's really as simple as open then, get a little banter back and forth, ask where they're going that night, they'll tell you, then you can either say "oh yeah I've heard about that place, what's it like?" Now they'll either invite to come with and find out, or tell you that it's this awesome place (why would they be going there otherwise?) now you just say something like "that sounds cool, ok I'm gonna see if you guys are right and tag along for one drink" the one drink is kind of a false time constraint, so they don't expect you to be hanging around all night, which you won't, because you'll be off gaming

Of course none of that is set in stone but in my opinion it's a much better way to go about it rather than "let me come with you and I'll buy you drinks then promise to leave you alone because there's no way you'd wanna spend anymore time with me" plus when you buy said drinks, everyone at the bar will see you buying drinks for girls and then watch them walk away from you.

I didn't say you were trying to fuck these girls. You're just using them to create an image for yourself.

So by being a normal dude who's cool to hang out with spending a mere 12-20 bucks (maybe once a week if you want) you can create a pretty bad ass image of yourself in the eyes of other people.

Instead of a guy walking in by himself... You're now a guy walking in with 3 girls.

Instead of a guy ordering drinks by himself... You're now a guy ordering drinks with 3 girls.

Straight up, one of the best ways to go out and get laid is to have another girl with you. This is a simple way to make 3 new girls your friend for the night.