I have a background in writing technical papers for an industry I worked in prior to moving to another form of engineering within the same scape. Don't use an editor, but use a professional cover service.
I read any long work, >20,000 words out loud, on the potty, sitting in a bath, and play back my own recording when I'm cooking or cleaning the house (I use headphones for this because vacuuming). I've found this is a great way to spot errors and rereading the same thing a few times over line by line and thinking about it before moving on works out for me.
The only complaint I got was a bad name misspelling John to Jon a couple times, and writing a romance novella set in 1990s London but overlooking using British English and general terminology. Basically a dumb mistake to overlook something so critical.
I probably go over each work 20-30 times.