How many hot stones do you use........
I think it depends on how you use them.
I use two foot, two hand, sacrum and belly stones...theres 6 there.
2-3 pair large stones
3-4 pair medium stones
3 pair small stones
And you are re-using them throughout the session - putting them back in the heater and taking out a fresh hot pair.
plus finger and toe stones if you use them
I don't use the small facial stones much.
So - it matters MORE that you have the correct sizes.
I do recommend taking a GOOD class.
The Hot Stone massages that I have gotten from untrained (except for a video) therapists have not been very good. But I know that there are some therapists out there that seem to be "naturals" at this. In general - hands on training gives you better knowledge about safety, contraindications, proper care of equipment, and a much better feel for what it SHOULD feel like - both temperature and technique.