Being a Chinese I am, I have tried gua-sha treatment a few times, done my by aunt who is a beautician with real knowledge of this treatment.
Traditionally, it is meant to ‘scrap away’ any heat or knots in your body. And also to improve blood circulation. The first tool that I knw was used was usually ceramic spoon, and then fork.
The result of gua-sha, and usually will subside after 2 days.
I have a tool at home myself, but I don’t usually use it unless I am suffering from bodyache, but of course, my pressure will not be as strong as the professional.