Is there any calibre that is a real "brush buster"? I don't think the calibre is as important as the style of firearm. The lever action is as good as it gets for thick, tight areas. I find myself using a 3" 12 ga. slug in a 22" rifled barrel Rem. 870. I like this setup because it anchors a deer up close and you don't have to guess where it went.
I agree that type of action is better than style of bullet for busting brush. My son and I use a 30-30 Marlin 336C and 30-06 autoloader for heavy dense cover. Bolt action comes into play for more open territory.
When it comes to scent, there are basically two types; those that attract and those that mask. I've tried both on many occasions. There are lots and lots of "doe in heat" scents, designed to attract a big buck into range. I've also used a "cow in heat" scent while elk hunting.
Another scent would almost be better named as a "coverup smell". The main goal is to cover up human odor or mask it. Though I don't believe you can ever totally eliminate all human...