I know that Dr. Mew is big into the chin tuck for potentially creating some outward pressure applied to the airway.  No doubt, posture is one important element.  For light, intermittant airway pressure, I think playing a musical isntrument is a more targeted approach that doesn't risk insufficient oxygenation.  It also has a number of studies behind it.  However, I wanted to share my favorite nasal clearing exercise.  This has not been studied within the context of OSA as far as I'm aware, but there is excellent information from the Eastern philosophies to breathwork, including nasal breathing exercises.  In fact, a Hindu friend of mine had taking me to a breathing club of sorts.  People were telling stories of ending additions, behavioral changes and the sort!  It was so strange to me and seemed like a drink-the-koolade type group.  It was so weird and I just didn't understand.  People were super hip on good posture for meditation and even certain breathing exercises.  Now, it makes more sense.  Here's one of my top favorite:

https://www.youtube.com/watch?v=oyn2LiHgCPE&t=16s

In this video, she goes rather slow... but I like the explanation.  I truely believe that this is a foundational key to nasal breathing on a consistent basis.