If I understand you you are not talking about angled entries but angle casts right? Tune up drill is great for working on angles entries and lines but not for teaching angled casts. After swim by I usually work on some really easy pattern blind with some whistle stops in them. Then I will set up a 3 pole blind. Three pattern blinds with a short swim and maybe 30-40 yards total with a 10-15 yards swim. Equal length and about 10-15 yards apart. Make sure the piles are well marked, I like to use something white like a Clorox jug on a stake. First mark then line each one. Then when confident send to the middle, do a whistle stop in the water and give a angle back but a big angle. You are going to use contrition to get him to one of the side marks. Then line the middle mark. Then try the same angle again. You might need to use overs. After a while the dog will understand that the left angle back means pick a bumper up from the left pile. It is basically a three hand casting drill in the water. Don't put too much pressure on the dog in the water or to many whistle stops. baby steps. Also make sure the dog is doing angles on land well first. You can do this with just two piles as well but I like setting all three up, and master one at a time. Also wait until the water is warm. If it goes really bad just throw a bumper to the pile.
Gee, I've read this a few times and, even though it's not that clearly explained (and Nate obviously meant "attrition" instead of "contrition), the underlying principles seem sound and compatible to what I think Angie is offering. Tune-up drills can be of varied complexities, depending on the dog, from simple "get in the water" blinds to angles and re-entries. Presuming sound basics on land that have included teaching angle casts on land, both Angie and Nate are proposing casting the dog off of one taught blind to another in the water to teach angles. Angie is further offering what Lardy terms "definitive casting" by handling the dog on the return.
Good stuff all and what I have tried to do to varied success with mine.