The way I look at the diamond penalty kill is as either an aggressive in zone penalty kill to attempt to score where I would send my top guy as a receiver in football (american) to receive a home run pass from any of the other three defenders (if I'm down a goal). Or set up against an umbrella power play in the defensive zone to off set the shooters on the outside.
Your forecheck can take on whatever you want, aggressive (if you need a goal), 1-1-2, etc. Once your back in your defensive zone your setup again is what you are looking for out of it.
If they set up in a umbrella or a 1-3-1 diamond pplay then you need to use a diamond pk. The players in the video do this.
Most NHL teams have the forward on the puck side swing into the middle to force the puck up the boards and into the other forward on the weak side. When they pass the puck back the other forward swings and forces the puck up the other way.
Once in the zone you have to decideif you are going to pressure or contain. The defensive hockey booklet in the files section of this site has a lot of good pk info.