How and when do I do this? If I cut at an angel, I've read where you should cut a 45 degree chamfer around the edge of the cut to promote growth from there. If I do that, do I cover all or part of the cuts with cut paste. And what do I do about the suckers. Do I leave them? Cut them all off? Cut some of them off. Please, full instructions on how to proceed would really be appreciated. Thank you.
As always, a picture will increase the quality of the responses you get.
I'm not certain what you mean by 45º chamfer. Ordinarily, when chopping a deciduous tree, experience dictates making the chop and coming back later to angle it out so that there is a smooth transition. Crape myrtles are somewhat of an exception as they're looking for an excuse to bud out and will usually be pretty reliable in throwing a bud toward the top of your cut. With the poor health this tree has to be in, I might recommend the more traditional/safe approach of cutting it flat across though.
I'd recommend covering all the exposed wood with a cut paste while the scar is healing over. I can't intelligently offer advice on the suckers without a picture.
Let's see it.