If I could teach only one stroke to other massage therapists, it would be Russian circular heel of the hand friction.
Friction is seldom used in Swedish massage but used quite a bit in Russian massage. It's a great stroke and I consider it my "workhorse." I incorporate it liberally during full-body relaxation massage because it's relaxing and feels very good. It's great for muscles that are tight and sore. It's particularly useful with athletes. It's my favorite stroke.
Done properly, it's very comfortable for the client and very easy on the therapist. Remember not to do it too fast. It should be done at a moderate to slow pace. Too fast will take the sensation of depth out of it. Oil should be minimum, just enough to let you move along easily but not so much that you are sliding over the skin. There should still be a little friction.
Will Stewart of 3-D Optimal Performance and I teamed up to produce this brief demonstration of Russian circular heel of the hand friction. Try it and tell me how you and your clients like it!