Ahh Grasshoppah...practice...much practice. Along with a well fitting shotgun. Some pull two, three or four from their belt with the left hand and load over the top. Some pull single shells with their right hand and load from the right side and some pull two with the right hand, load one, shoot and then slide the second in. The last is the most fool proof and the quickest method IMO. That's the way that Holy Terror is currently doing it. If you are loading from the right then I have found that a shorter than usual stock helps. Rather than fitting the stcok so that your index finger hits the trigger when the end of the stock is in the crook of your arm I like mine so that when I have the gun up to my shoulder my fingers lay well over the port of the gun. This allows me to easily slap my shells in the open port. I just recently cut my stock off another half an inch and that small amount of difference stops that last little push with my thumb to get the shell in. That has cut down on fumbles and on time.
Maybe I'll take the video camera tomorrow.