I've started recommending, when I beta read for authors, that they "narration strip" their chapters to check for both internal and external dialogue flow.
This is a technique, or an editing tool, if you can call it that, that I stole from screenwriting and screenplay reading.
For a while, we were big Downton Abbey watchers and my husband found the books of seasons 1-3 scripts.
In both examples, virtually everything -- plot, setting, characterization -- is conveyed via dialogue, and external dialogue (with the exception of soliloquies in Doescher's works), at that.
I decided to use this format with my MS to help in certain sections where I've always struggled to write good, convincing dialogue.
Steps to Narration Strip your MS / or a Scene in your MS:
1. Identify the section of your novel you want to focus on. It can be pages, or a page. The length is up to you.
2. Copy it and put it in a separate document. You're going to work with it "off doc," or "out of doc."
3. With the new doc, strip -- delete -- every ounce of narration, until you're down to nothing but what's between the quotes.
a) Can you tell who's talking, without the dialogue tags? If not, you may need to do more to convey character in your dialogue.
b) Does the dialogue makes sense? Does the dialogue skip around? Did you edit and move something, and not consider you needed to rewrite? If so, rewrite.
c) Does it flow? Or does a character ask questions, and never get answers (the rhetorical-questioner?)? Do subjects just change, randomly? Or is there a logical progression to the conversation?
Rewrite until it all flows.
Then take all that narration you stripped, and determine what you want to keep.
Rewrite again, because you're going to find you probably don't need quite the narration you had originally.
Pop it back into the MS, by copy and paste.
I've done this several times, and it works like a charm! I'm not saying it isn't difficult, but it does help, and it helps to have a mentor text -- an example of some great, flowing character-filled dialogue nearby when you do your evaluation.