I'm with what Anney and Evan have described. In T-work my dogs learn to change direction (those momentum casts), and then as I develop their skills we move more and more to literal casting. Now in training, I expect Breeze to take literal casts and use attrition and other corrections as merited when she does not. When we are really in tune I have to be very careful not to overcast as she will really take what I give her--I practiced in a mirror so I could see what she sees and get a feel for the positioning.
In a test, I have to read the factors influencing the dog, and there I will use the cast I need to effect the necessary change. More often than not now that is still a literal cast for Breeze, but there are still situations when I will give her a little more to get her out of potential trouble. In her title leg test for her Master, the water blind skimmed over the tip of a point. Quite a number of dogs had hit the point and then sucked in behind it, towards where a mark had been. Some of the other handlers had stopped their dogs on the point and given them big angles (read, near-overs) off that point. I gave her a bigger angle than what was the true literal cast to the blind, but not near as big as some other handlers had done with their dogs because I knew that she would take most of it, and I did end up having to give one more corrective cast the other way to put her right on the bird at the end, so I probably could have gotten away with given her a smidge less than I had--but in the moment I gave it I wanted her out of that suction, and to avoid the fights too many had already had getting their dogs off that point (I watched 4 consecutive dogs fail that blind!)
Some of the HRC guys I see still use momentum casting. even in a test, but I just don't like it because I hate messing with a dog's momentum if I don't have to--that is one beauty of a dog who will take literal casts--you can let them roll!