How to turn friend into friend with benefits?

I have been a client of a mage therapist for over twelve years and I get a mage from her every week. During that time we have also developed a friendship even though our attitudes about life and our interests are very different. Occasionally we go to a restaurant to eat (I normally pay) or go to a movie together. During mages she always ensures that I am properly dd even though I would prefer to be without any top sheet at all. But after all of this time I would like to ratchet it up a notch and become friends with benefits. It wouldn't be something that we would do all the time, but once in a while would be nice. I know she is not dating anyone else and I know that neither of us want a romantic relationship, but at the same time I'd like for us to share a bed occasionally and have some level of ual interaction if for no other reason then to scratch an itch. So far she is opposed to this and won't even really discuss it. I'm at a loss on how to make any progress, but I don't want her to think that I am applying any pressure because I don't want to lose her as a friend. What's a guy to do?