Willieks technique is certainly a good one. As an alternative, but in a similar vein... and assuming you are a right handed shooter... Carry the rifle on your right shoulder with the barrel facing up. When walking you should keep your right hand on the pistol grip with your fingers facing towards the buttstock. For a quick shot you bring the rifle around, pivoting on your right hand... the barrel swings behind you, then down and around until it is facing the direction you want to shoot. Grab the forestock with your left hand and you're in position. I simultaneously kneel down with my right foot under my butt and my left knee providing a brace for my left arm. It takes some practice to be proficient, but it works very nicely once you have developed a fluid technique.
I will tend to alternate between this and willieks technique in order to alternate the weight bearing between my right and left shoulder.
That said, I have more recently gotten hooked on the safari sling. As mentioned, it is not as good when hunting with someone on your left side, but otherwise it is fantastic.