I guess I don't have anything original to say, but:
I like the story a lot. It flows smoothly, both in plot and in narration style.
Coby is amusing, cute, with a dash of egocentrism - yep, a
red fox all right.
As of Flynn, he follows the best tradition of a Spark, at least the kid-friendly ones.
And their quarreling between the two protagonists...well, best tradition of literature and movie industry, the rare kind of trope that's usually still funny (and very funny in here).
The "... and occasional odd bit of welding" passage reminded me of sounds in cartoons when a mad contraption is built offscreen or inside a cloud of dust.
Alcoholic dragon is a new, at least to me. Amusing, and surprisingly fitting.
Hope you plan to write more about them two.