"I still maintain that given the correct measures it is possible to keep deadwood on diciduous trees free from rotting as any other tree we keep as bonsai. We have the luxery of controlling the moisture as well as where we water the tree. Watering the trunk everyday on the deadwood would probably not be a smart thing to do. Of course it would not be very wise to do this on conifers as well. Moss is the number one killer of deadwood in all of bonsai."
I actually have quite a bit of deadwood on my Amur maples. If you have amurs, deadwood comes wiht the territory. They die back with heavy pruning. That means an ever-shifting design process as dedwod melts away over the years.
One of mine is completely hollow-- another has significant self-imposed shari. I haven't treated either with anything and I don't plan to. Stark white deadwood on maples is jarring. It doesn't happen in my local environment. Deadwood on decidous in ground trees around here is usually blackish grey, or brown stained with algae and moss and sometimes mushy and wormeaten. If you want deadwood on a maple don't aim for the pristine, alpine white spires and snags you see on conifers...
For may maples, I let nature take its course. Maples heal pretty quickly, or they don't. Adding lime sulphur and preservatives can actually be a bad thing, but I'll get to that later.
Controlling moisture on bonsai in my neck of the woods it is a pipedream. Moss is not a significant problem. It is easily removed. The problem here in the East and South is water. From the rain in the spring, summer thunderstorms and fall storms (ever try to keep a tree dry in a heavy Nor'easter or worse-- a hurricane?), to the snow and clinging ice load in the winter-- deadwood faces alot of uncontrolled moisture in these parts. Add in summer humidity that prevents stuff from drying effectively for six months and you get rot--a lot of rot.
I have tried lime sulphur, minwax wood hardener, etc. on maple deadwood. Usually such treated wood becomes a hard shell of funny looking plasticized white wood over a mushy rotted shell of decomposed wood underneath. Using wood hardener can actually accelerate the decay process by trapping moisture underneath the hardened wood. It doesn't stop moisture penetration in a lot of cases, from seeping in from other directions, though. The process can take five or six years, but it's inexorable on maples. There are other deciduous and broad leaved trees that don't rot very fast, though.
Boxwood is one. Black cherry (prunus resinosa) too--primarily because it has high resin content like conifers do. It does, however, attract borers, which home in on the scent of deadwood on trees.