What I do to mix priming solution is put it in the bucket first, then rack into the bucket. That's it.
Caramel/crystal malts can aid in head retention, as can just a touch of wheat DME or LME (or wheat itself if you're mashing). Try replacing .5-1 # of the base DME (or LME) for wheat DME (or LME)
Just a thought, but as to the head retention thing, how do you clean your beer glasses?