3 skills
A Proofread That Leaves Your Voice Alone
Run the checker last, accept one suggestion at a time, and know which four categories of suggestion to argue with.
Boil a Long Source Down Without Bending It
Pick the output shape by what you need next, feed it clean text section by section, and catch the hedged finding that came back as a fact.
Rewrite a Passage Without Losing What It Said
Paraphrase a paragraph at a time, lock the terms that must not move, and check that the claim which came out is the claim that went in.