Also with the dormant buds on the trunk you speak of, are they generally always visible?
No! After a few years any dormant buds virtually disappear. You can see them on 1 yo wood and you can generally see the ring where the nodes are on 2, 3 and sometimes 4yo wood but after that it gets far more difficult to pick. On older wood you need to have faith and maybe some imagination. As I said earlier, all trunks started out as a seedling which had leaves and nodes around 2-4 cm apart. As the tree grows those nodes STAY WHERE THEY WERE. They don't get further apart, or move up the trunk. The trunk just gets fatter. Everything else - scars, branches and those nodes, stay right where they started out.
I have seen occasions where really old wood has failed to produce buds where there should be some but generally with the trees we are cutting back hard there will still be enough viable buds for the trunk to sprout.
I'm a little reluctant to cut the roots clean off because there are no fine roots up high at all.. You think that won't be an issue for it?
If you've had a look at the thread Dansai has offered you'll see that tridents don't need to have any fine roots where you prune roots. All my field grown tridents are treated like that at some stage and I expect a 99.9% survival rate. If this was one of my trees I would have no hesitation in cutting all those roots right above where they turn downward - but this is not my tree, it is yours. If you want to go the long, slow, more comforting way and layer each root or take a few years with the alternative method Bodhi has offered please be my guest. All of them work but YOU need to be comfortable with the whole process. I've just offered an alternative that I know works for me.
I would be best to do it in August before bud burst?
Here, in NE VIC I can cut both roots and trunks anytime from mid winter through to bud burst and be sure of a successful outcome. I have also cut back tridents in summer and they still respond, just a bit quicker. I do try to avoid the period just before bud burst through to a few weeks later when the leaves have hardened a bit. Seems maples bleed profusely at that time and don't heal very well. Note that if you cut a maple and it does start to bleed a lot (not just a few dribbles) a quick root prune usually stops the bleeding.
Can't vouch for the truth of that info though - it just seemed like a good excuse to save some time and resources by not using any 
