One note of caution.
I would recommend NOT tightening the drag all the way down. Reason, with a heavy flipping stick and 50 lb braid, I have seen times where you will actually tear the mouth if hooked in a softer area, fish shakes his head and it's off. I had this problem when I started flippin, I'd cross their eyes, get em free of the cover, they shake and next thing they were off. I solved it by loosening up on the drag.
When to flip: Flipping is simply a technique to get a bait into heavy cover, quietly, and with little or no commotion. With that being said, the technique is probably most effective when fish are in cover, such as when the sun is up and the sky is bright.
Don't forget to try other presentations in the early morning or in the evening, the fish may be a little away from the cover due to light penetraion being low.