Wanderer,
Just my 2 sense here so take it for what its worth. You speak of getting to know an area and your right, if you cant glass and or scout it out to see what they are doing in Aug then its tough. You are correct, not much bugling so that limits the location finding ability to usually on the foot. If you know where the rubs are at then chances are you are very close to the perfect spot or transition area catching them moving from feed, water to bed. IMO we as hunters get stuck in the idea of thinking I have to hear them to find em. Yes it helps and makes for better stories and is a lot of fun, but in Colorado you have to use the hunter pressure to your advantage and figure out where they are gonna go next. You mention the dark timber. There is a reason old timers used to always hunt rifle and still do with a short barrel lever action, high scope mounts and a 3-9x. Easy swing in the darkest nastiest stuff you have ever seen. It sounds like you are in the right spot. Sorry for the campfire rambling. To answer your question. My game plan consists of hunting wallows, water and rub areas with a MT decoy, cow call and zero bugling from a human, opener till roughly 8 Sept usually around 10k feet. 8-9 Sept till opener of muzzle maybe a location bugle if I hear them other wise nothing but cow calls. Muzzle opener till 15th you have to re-pattern them or know where they are gonna go and get there before they do or intercept them on the way. Post muzzle they start to get vocal and the hunting usually turns into something like on tv. Ive pretty much describes my GMU in Co that my family and I archery and muzzle hunt. Pretty much the same applies all over the state, just have to figure out where its happening. Weather though can be the gamechanger. We have drug a screaming bull 600 yards across an opening when it was cold and raining before about Sept 5. I like the opening week because that's IMO your best chance for a bigger bull on public land. or shear numbers of animals moving around its tough to bet the second week as the searching and moving really starts. Pm me about your GMU and I may be able to give you some more area specific details.