I think the Coral Bark makes a much better tree than a bonsai. I havr about 40 Japanese maples, about half a dozen of them I would consider good bonsai materiel. Just my 2 cents.
First flush of growth after cut back. Now do I want to let all the new branches thicken up and then reduce? Or keep lots of little growth and pinch back two each set of nodes all season long
Coral bark tend to send multiple shoots from each node. I would go through and thin it out just a little. keep no more then one or two shoots coming from one spot. Let everything else grow the rest of the season.