Can't honestly say anything about a decoy as it just doesn't feel like it's a necessary item to pack around (unless you plan to bowhunt them). We typically hunt goats mid September when the rut seems to be going along fairly well but it sounds like you're looking at mid to late October to chase goats and the rut will probably be over by then. It seems to me that the white t-shirt trick works during the rut when a buck has been chased out of a harem and is moving on. Other times the herd buck will be curious enough to take a look but then go gather his girls and leave.
As for pressure, I personally don't think it affects the hunting all that much. We almost always hunt the first week of the season and have been really sucessful. As for goats being skittish I think there are two things to think about. The first is if the goats are somewhat near ranches, well traveled dirt roads, small towns, etc. they seam to tolerate people and/or vehicles better but get way out in the middle of BLM where they rarely see folks, then they tend to bust out easy. No worries though, they really don't run all that far and you can usually get out of your rig, hoof it and find them in the general area. The second item I think busts goats out more than anything is a white vehicle. Unless you have snow on the ground a white vehicle seems to make them run from a long ways off. Had one the first year we hunted Wyoming and they ran alot. From then on my dark gray pickup really seemed to make them easier to approach. By the end of October they should be pretty well bunched up and when you locate the heard there's probably a hundred or so goat eyes to contend with which will make it all the more challenging.
If I ever draw a deer and goat tag again in the same year I'll hunt them late just for the sake of a different challenge. Goats are probably my favorite animal to hunt and they taste dang good to boot!
Hope this helps.
Todd.
