This technique for removing cockblocks can work on guys you just met, or on guys who have been friends for a long time, it's useful because they probably wont think of you as a dick and they will be completely shut out.
The idea behind the technique is that people are very self conscious and things we say can effect how people think of themselves which in turn effects how they act.
Let's say we have a friend who we go out clubbing with once a week, every time you get close to closing he jumps into the set and steals your girl. You can't call him out because he's your friend and you don't want to do that.
So how do we remove our cockblock friend without appearing to be a major douche to him? Just pull him aside (usually should be done away from the club, bar, or any spot you are going to be trying to get chicks in) and tell him that he talks to much. You telling him he talks to much will sit in the back of his mind, he may forget about it in 5 minutes and go right back to being the cockblock he was but it's still there, and all we have to do now is refresh it every time we want him to shut the fuck up. If he jumps into one of your sets again and is trying to ruin it just turn to him and say "Bro remember our discussion earlier?" if he doesn't leave the group at the very least he won't be talking much if at all for the next few minutes.