Thank you Kabbie, your advice is appreciated. In fact, shortly after I posted this we were discussing it in guild chat and some of our regular M+ runners said the same thing. But it will take time, and he suggested a static group.
My problem will be to find a group that also want to do this that actually are online the same time I am. Too often my previous static groups have fallen apart because of timing. I normally cannot play late due to real life obligations.