I have advice that has been shared with me from others in our group:

Patience, patience, patience.

This advice is helping me immensely - I simply do small things or make short statements once in a while related to this form of interaction between us. He is taking the time he needs to get acclimated to the idea that his wife isn't quite the person he thought she was (for over 20 years!) and I am practicing patience. The neat thing is that my anticipation for those times that he does exercise his dominant traits has settled into a nice simmer inside that feels submissive in and of itself.

I also read, I think in The Loving Dominant, a list of traits that indicate you may be a possible dominant. The first and most important one was: do you take a lot of pleasure from pleasing your partner to the point that their pleasure is almost more important than your own? (Not an exact quote, but that was the gist of it.) That gave me a nice boost of hope, because it describes my husband. It seems almost counter-intuitive, doesn't it?