I think we talked about this some last year and there is certainly a different approach for trees in different levels of development. I generally use the "hedge" method on most of my Maples because I am still trying to develop trunks, and/ or just starting to develop branches... Thickening is what I want! Most of the trees you have seem to be farther along and in need of refinement not rapid thickening, and your method of removing the central bud slows the Spring explosion of growth a bit, leads to finer, twiggy growth and is perfectly suitable- obviously- for your trees! The results speak to that!
As for the timing Judy - let it get nice and shaggy! About 4-5 internodes+, then cut the branches back to right about the first or second internode of new growth. (I think WP says he literally HEDGES the tree, but I usually still prune each branch independently with the overall shape of the crown in mind...) Obviously, if there are sacrifice branches or areas of the tree you want to thicken more than others, heal a wound... Leave those branches alone, and "hedge" the rest of the tree... Repeat again as often as the tree needs it during the growing season. If this is a developing tree you want to expand the crown on a bit, get a thicker trunk, heal some wounds, thicken some branches... This is a great method! If your tree is in refinement stage like Mach's- slowing the growth by pinching Spring buds seems the best/ most commonly recommended technique!
I did pinch some buds this year on a Red Maple I have that has been in training for years, and I am doing my best to minimize the coarse growth and promote some ramification, especially in the top. I also pruned the heavy branches back to the lowest buds right at the base of the branch on some spots where the first internode is too long, basically starting the secondary growth over with- HOPEFULLY- two small twigs instead of one long, thick one... I am still firmly trying to convince myself that Palmatum technique will work on Rubrum!
I cut back (or not) by just looking at different parts of the tree and what stage they are in. What I need to grow longer and what I need to hold back. It's important, I think, to let your tree be a tree and put on some growth and not constantly pinch it back at least everywhere. It will keep your tree healthy.
