The above paragraph appears in every single Shell Center lesson. It's how they recommend giving feedback to students.
"Help students to make further progress by summarizing their difficulties as a series of questions."They don't suggest that you correct their work for them.
They don't suggest that you give students an answer key so that they can reflectively analyze their earlier work.
What they suggest, instead, is to treat a piece of written student work the same way that you'd treat any student idea. Ask a question, give them some time to stew on it. Give them a chance to improve, not in a week when they sign up for a reassessment, but right then, on the same problem that they had trouble with. Don't take away the chance for them to make progress by giving them the answer key.
The changes that I've made to the way I give feedback on quizzes are an explicit attempt to mimic the Shell Center recommendations. I collect the quizzes, I make a copy of them, I use the copy for my own record-keeping needs, and I give them back their original with questions the next day. I just hope that I'm making Malcolm Swan proud.