Okay this really deserves a better comment but whatever, I'm not going to get the better comment done. You already know most of the visualisation stuff, so my advice here is to target it physiologically: break out the heat. Preferably actual physical heat, not compounds like arnica or capsaicin, so you probably are looking at the adhesive chemical patches -- you'll want something small enough you can keep them on JUST the upper traps that you're trying to get to disengage already.

Heat interferes with muscle function; at higher temperatures, the muscle fibers stop being able to contract efficiently (or, you know, at all if it gets high enough but at that point you're probably looking at burns so, uh, not ideal). The reason you want physical heat is that it is at best an open question whether you'll get any of or how much of the same physiological effects on the muscle from applying something the nervous system interprets as heat as opposed to an actual rise in temperature. Meanwhile, I can tell you I have personally DONE the experiments on animal muscle tissue that show the effects of heat vs. cold and heat absolutely impairs muscle function.

This is, incidentally, WHY heat helps with tight muscles, something I literally never knew until I took Animal Physiology as a lab. It didn't even come up in the AP lecture class, much less any of my classes for massage therapy that covered muscle physiology.