Thanks for all the input!
I tried the little Wagner unit Paul suggested. I never thought it could really work, thanks Paul! As Mark mentioned I got some sense of spraying raindrops, but darned if it didn't do a great job. Went down just slightly lumpy but very consistent, then levelled out perfectly. Got the best single coat results ever, excellent surface cover and no issues with overlaps. Got a very subtle 2 coat result without objectionable gloss or filling in the canvas texture.
Very fast too, 4" x 40" strokes in just about 4 seconds with the nozzle almost as fine as it would go. It needs about 2 or 3 seconds from the git-go to start picking up the spray, important not to get ahead of it in that respect, keep the trigger punched between swipes. Bottom line is I think speed of application is the key to getting good results with these protective sprays, you don't want differential drying on adjacent swipes which is what makes rolling such a pain (for me).
Used straight Clearnshield "C" out of the can. Wonder if diluting would produce finer droplets...although why mess with success? Also noticed this unit has a $99 big brother with a separate turbine unit connected to a smaller gun with a hose, anybody using that?
I'm definitely feeling good about this. In the mean time I'm saving all those much-appreciated links, maybe I'll go on to something better but only if the Wagner is too short lived. It's so wonderfully compact, a perfect match for my tiny shop.