Trunk are thickened by every leaf. Each leaf thickens all the wood below it. The leaves up to 9" thicken the trunk up to 9", and same applies to branches: all the leafs on a branch thicken that branch and the trunk below that branch. So, leave all foliage on until it turns color in autumn and then chop to a point where you want to taper. Cut the trunk at an angle, ~45° to 60° on the rear of trunk. If you can wire a branch vertically at that point, so much the better. Do that every year to accumulate taper for the whole length of the trunk.
You will have a continuing problem deciding when to keep branches. All that you keep will contribute to girth, but at the expense of leaving wounds when excised. If you leave a branch on from the start of taper training (as above) it will be out of scale sooner, or later. The branches on forests need to be considerably thinner and shorter than non-forests to look right. Ultimately, you will need to remove all branches that are thicker than branches below them, and grow new branches higher up. DR will bud out all over the trunk, continuously, so that's easier than it sounds. When you start to get close to finished appearance you may want to trim off all the branches and grow new ones. That's easier than it sounds, too. You can do it in steps: choose some specific length of trunk that will be the lowest couple ranks of branches; keep branches which are in good locations and not too heavy, and remove all others in that section; do the same in successive years, moving up the tree, section-by-section. That way, (from the bottom) each rank of branches will be older and larger than the branches above by about one year's growth, per rank.
To develop finished foliage fans, let grow a given fan except allow nothing growing straight up or down. In mid August, trim all leaves back to 3 or 4 buds. There are many buds in the axils of individual needles, one bud per leaf/needle. (I have a problem calling soft foliage "needles".) It will be too late in the season for new growth to start in response to your trimming. Next seasons growth will be just right. You need to apply these foliage trimming methods every year. It makes the finished trees show-able in spring and autumn, but looking semi-ratty in mid-summer. Constant clip-and-grow thru summer will just encourage more budding out where you just trimmed and all over, too, and especially at the ends of branches and will develop a knot of buds/foliage at the end of a relatively skinny branch, which looks stupid. It's better to let the existing too-long growth to get longer and trim back in August. That kills a few birds with one stone: growing foliage in a horizontal fan to become next year's twig, thence the following year's extended branch, all of which will be easier to keep in a horizontal fan; and preventing knots of buds with twigs sticking out in all directions; and allow you to trim the maximum volume of foliage each year to keep the tree ~dwarfed while maintaining profile.
It is more important to keep the trees/branches/foliage fans in-scale than to grow it bigger. Eventually, you'll be happy with how it looks and be able show it for years and years before you need to worry about stopping it from becoming too big.
