After posting my recommendation for the use of a copy editor for the dissertation, I came across a wonderful piece published in the advice section of The Chronicle of Higher Ed by Rachel Herrmann:

Over the past six months I’ve discovered that editing my terrible, horrible, no good, very bad dissertation is very similar to confronting an array of ingredients that you must turn into a meal. Sometimes you create something so great that you can tell almost everyone will like it. During other moments you realize you need to modify your concoction before you present it to others. And every so often you know that you need to throw it all away and start over.

For those who do not have a subscription, download a copy here: A Mess of Edits – Advice – The Chronicle of Higher Education