Everyone should do their own copy editing. They’re your words. You placed them there, you need to take the bad ones away or fix them. Why waste your editor budget on something you can do? Save that money for actual editing. Copy editing is a lot of work and should be done a few weeks before you send the book to your editor. It’s boring, tedious, and takes forever, but it has to be done.
Copy editing is reducing repeated words and phrases, removing amateur words, fixing homonyms, replacing adverbs (telling) with vivid emotional descriptions, etc.