Can you elaborate on what exactly you did to ease through the unwanted Valsalva maneuver? The hypothesis seems to describe pretty accurately what I feel when I stutter and get blocks, but information doesn't seem to be exactly abundant on the topic of actual therapy and excercises for improvement, although I did find the channel of William Parry, which has some information, most notably using humming and training to eventually be able to force the glottis open at will without actually humming, in normal speech (which he called "modified humtonian speech", which sounds a bit absurd considering he spoke out against modified speech technique's in the video, but I digress).