In a niteclub or a spectator event, the last thing that you want to do is attract attention. You don't want to bob and weave without a punch to bob or weave from. Punchless bobbing and weaving attracts attention from the opponent's friends and from security, or even cheap shotters from the gallery. Pulling out a gun or a knife will attract attention too. That's to be avoided. In CA it's a good way to get into the inmate dating scene anyway. Pulling out
a knife or a gun can raise something from a little brawl to a killing.
Getting your *** kicked ain't worth killing someone over.
The next thing is that you don't want to grapple if you can avoid it. Where the crowd is thick you want to end things quickly. If you go to the ground for the most part you WILL get stomped and most of the time the opponents friends WILL kick you and they don't care about kicking their friend in an effort to get you. Cheap shotters WILL hit and kick you for fun, and you'll be rollling around on broken glass or blacktop, puke or even urine. This is especially true if you are the security at a concert or niteclub.
A big guy needs room to swing for the most part. The big guys that don't need room to swing you should run from. They know what you do and better and they've got more meat behind their punches. If you can't run, then control balance, through trapping or breathing through short punches to the ribs underneath where the armpits are and slightly to the front or the point right underneath the sternum. These can control breathing and won't cause any permanent damage. Unless you have practice, don't go for a knockout punch or eyestrike to the face. It's high up on tall guys and you're exposed when you do it. Focus on what you've got. Look at targets that are easily reachable. Knees, solar plexus, stomach, bladder, groin, elbows, arms, neck. Hit those targets with the edge of the knuckles, or some other narrow surface and not a flat fist.
As for striking to the groin, the pain is not immediate, and most guys can keep going for a few seconds after being hit. That few seconds can be filled with quite a few punches aimed at you. Also after a few hits to the groin in the same fight, it stops getting any worse for the most part and it loses effect on them.
Don't let him grab you. If you do that, big guys are strong, in my case usually they're stronger than me. If they grab you, you have no choice but to do moves that attract attention. Also they often have longer reach and can hold onto you and hit you while you can't hit them back in the trunk or head with your arms.
Another thing at these places is drugs. A lot of big guys that I've had to deal with have been high on something. They don't feel pain the same way if they even feel it at all. They also don't care too much about being disfigured, even if you show them the skin, hair, or body art. With those guys, you have to control motion or breathing. That means broken bones, dislocations, chokeouts, or knockouts.
There's always more to it of course, but in my experience these are some guidelines. I think the bouncer guys Kenpo Yahoo was going to talk to my share some of my opinions.