Just like being good at “other” things you need to read the room, his energy and his reactions.
Start on his back with light pressure, gradually increase as you work through his lats, shoulders and the muscles parallel to the spine, as you feel him relax or hear pleasurable sounds coming from him you’re on the right track.
Just the fact that you are doing this is going to thrill him, does it need to be like the greatest professional sports massage, this is just extended foreplay and he will appreciate it so much.
There are lots of sensual massage videos on YouTube, just look up Tantric massage and you can get a few pointers but don’t do the whole routine because chances are he won’t like half of it, just get to know your lover and the rest will fall really into place.
Always keep a hand on him, make your motions slow and deliberate, jumping around adds unpredictability which isn’t pleasurable in this setting. Before you start ask him if there is anywhere he is either ticklish or doesn’t like to be touched and really respect it.
When he is on his back long slow movements over the chest and quads are typically the most pleasurable.