How important is precise carbonation level to you? If it is, avoid the 30 psi and shake it method.
You can end up over carbed or under carbed depending on the style. Set the pressure and let it sit refigerated at the pressure you've chosen to match the carbonation level for your storeage temp. Hey if you want to occasionally shake the keg to speed up the process, go ahead but don't exceed the pressure you've chosen to achieve the carbonation level you're targeting.
I'm drawing from a keg of Ordinary Bitter that has only got 3 pounds on it and the head and carbonation level are perfect.