I just walked in and shot as many people as I could in the head. Watch out for the last manager though because he usually runs out the back door and you have to chase him down in a car. If you have any grenades then throw a few of them in as far back as you can and take out the close people with a gun.

You got it right, silent kill the first guy and then go to the back wall of the club down near where you get private lapdances. Headshot the manager near you talking to a dancer on the right wall and then leg it out of the club through the back door, kill the guard by the dance rooms on your way out so you're not cut down. Grab any car and chase the third manager down in the street who'll have made a run for it in his car.

This is how I did it. It might not work first time, but it's a decent method IMO.

First obviously listen to all three conversations to get the locations of the managers. Then, go right to the back of the club (where there is a door frame that leads to the private rooms). There is a small bit of cover that is formed by a piece of guard rail thing. It's on the opposite side of where the door to the private rooms are. Get in cover there, pull out your gun and shoot the manager who is standing with the stripper in the main area. Take down the security one by one until the one in the private room runs through the main room, and gun him down. Now at this stage, the one in the office will make a break for it, so run out of the back entrance and run around and try and shoot him before he gets in his car. You can also shoot him through the windshield. You could probably just chase him if you wanted to.

There's probably better methods, but this is how I did it and it worked first time.

A tricky mission, I have to agree. Did it on the second try, though.

This is how I did it: I first killed the manager in the cabin silently. Then I found the second one talking to a stripper. I shot that one with the shotgun, died after the second shot. I then shot the third manager before he even had the chance to run away.
Just don't mind the security shooting at you. As soon as all three managers are dead, they leave you alone anyway.
Also, that way you can save yourself of the effort of having to chase him per car.

For this mission as soon as i walked in the strip club i shot my weapon so they would all run out, i hopped in a car then shot em down. Easy as can be

i got lucky with this one, i killed everyone in the club and ran outside, the other manager went into his car and was gonna drive away but hit another car giving me time to shoot him through the windscreen.

I failed the first time because the one manager just left real quick and I had no way of getting him. The second time I got the guy in the office but I had low health so I left the club, before I did anything I got all three on my radar. Niether manager tried to leave so I slowly fought my way to them.

I may have found the easiest method to beat this mission. I walked into the first room on the left with the intention of silently killing the manager with a bat but instead I let him hit me once and he ran out of the room. I waited about 10 seconds and then chased him to the back of the club where the other two managers were. All three made it through the back door of the club. By the time I made it outside all three managers were in the truck. I pulled out my machine gun and killed all three in the truck before they could drive anywhere.