I have never had a separated shoulder, so take my advice in that context. However, I have found that some injuries will heal very quickly if stimulated properly. The problem is that sometimes gravity and leverage make the proper stimulation difficult and even dangerous.
I will give a couple examples from my own experience...
I had a nagging shoulder injury for about 2 1/2 years, which I had tried to rehabilitate by various combinations of weight training and stretching. These did help, but only along particular lines of the injured area.
However, by holding a fairly heavy weight and "vibrating" it, or having it in some way shake, it seems that the injured areas could finally be reached and thus stimulated to heal. Healing only took 3 days after this discovery.
I have successfully used this technique several times since that discovery.
The "combat fitness" guru Matt Furey talks about using bands to achieve this vibrational effect, but I have found that free weights can also work. Although the idea is simple in theory, it is not so easy to carry out in practice. Shaking a weight around when slightly injured is a good way to drop the weight and get further injured. This is especially true when trying to rehabilitate a stronger body part (for instance, a stubborn muscle injury deep in the back). It is kind of dangerous to be shaking a few hundred pounds around a still-tender area. I had an ankle that took some ingenuity to figure out how to properly stimulate, but once stimulated it healed quickly. I have a nagging spot in my back that I was afraid to try to rehabilitate, but finally did, again using this shaking idea.
Light weights don't seem to have the same effect. I guess my recommendation would be to go and purchase a set of bands and then pull them enough so that your muscles start shaking from the exertion. I think that's what I'll do next time I need to rehabilitate, rather than dancing around with those killer weights.
My guess would be that the electro-stimulators would do a very good job, although I have no experience with them.