If you see only two girls among 20 dudes it means that some of the dudes already approached them and the girls were not responsive.Also if girls respond to you they may give green light to other guys to approach as well so they may be afraid.
Generally in these cases in my opinion a quick estimation of the environment is essential.Find out the best position and angle to approach the girls.With your back you should block sight to most other guys and make them lose optical contact with girls eyes.Even if you do this some guys will try to send signals to girls behind your back so always change position a bit.
After a while some may even come and push you or send the bartender to seve the girls so he will set you out of position for another guy to occupy this.Generally being felxible always works but some pushing is inevitable.
Generally in these cases in my opinion a quick estimation of the environment is essential.Find out the best position and angle to approach the girls.With your back you should block sight to most other guys and make them lose optical contact with girls eyes.Even if you do this some guys will try to send signals to girls behind your back so always change position a bit.
After a while some may even come and push you or send the bartender to seve the girls so he will set you out of position for another guy to occupy this.Generally being felxible always works but some pushing is inevitable.