Place a tennis ball against the wall at the height of the sore muscle, be it your upper back/shoulder blade, lower back.
Lean against the tennis ball and move side to side, up and down, or even in circles, whatever feels best.
You can even do this on the floor to massage the same areas and add the glutes, hamstrings, quads.
If you would like, I would be happy to help demonstrate and guide you.
