Jim is exactly correct... CM grow so fast that is much better to develop your branches and ramification through lots of pruning before ever trying to wire or shape.
Its seems counter intuitive but it works very well. Cut all those long branches to about 1" from the trunk(or where you would like the first branching to begin)...get rid of the wire. In a couple of weeks, where you are, they will have all shot out multiple new branches...let those extend to about 6 leaves and cut back to about an inch again. Repeat as often as you can through the growing season.
The original branches will thicken and develop some nice ramification simultaneously. In two seasons you will have a "bush" with lots of branches that ramify close to the trunk...and the leaves will be much smaller. At that point you can selectively prune and wire to create a really nice bonsai.
Personally I find that putting them in a bonsai pot/soil slows down their development drastically...while I am developing branches I maintain CM in nursery containers and a nursery mix. Only when I think the tree is ready for maintenance and past the development stage does it get put into a bonsai container...the exception to this are mame size trees.
I find that I have to offer CM much more winter protection than my other trees...if not I lose branches...especially with the dwarf cultivars.
I find most people are immune to experienced advice when it comes to growing trees. They ask questions but do there own thing anyhow...If you have more than one of these, try this advice on one tree, grow the others your way...then compare after about 2-3 seasons and see which tree is further along and looks better. (I am generalizing this sentiment and it is not intended to be pointed just at you...yet)
Prune, Prune, Prune...it makes a huge difference....only took me about 10 years to figure this out because I am smarter than all those old codgers
Good luck with your tree! I hope it turns into something fabulous.
John
