Most math textbooks are full of proofs of theorems and examples solving problems. This is not better than direct feedback from an expert on your own proofs (e.g

Most math textbooks are full of proofs of theorems and examples solving problems. This is not better than direct feedback from an expert on your own proofs (e.g. a tutor, professor, or TA), but it is in my opinion exactly what you are talking about. Students should read the proofs and the examples, and try it themselves until they really understand it. Then the exercises usually fall into place.