Ok, this was "Yet Another Cool Idea" that I just had to do, so I scooted over to Home Depot, picked up the pump sprayer and the A176 fitting, then hit my LHBS (which conveniently is between my home and HD) to pick up a Firestone ball lock beer post with 5/8" -18 threads, a universal poppet (two thumbs up on the latter!) and a fresh post O-Ring, and as soon as I got home put the whole works together.
First assembly attempt I put the white rubber gasket thingie removed from the original nozzle in the same orientation into the brass fitting. That turned out to be backward and did nothing to seal the trigger nozzle tip, so I flipped it over. Et voila! The trigger works perfectly, the post seals tight, and the poppet works just fine with my QDs.
The A176 thread isn't exactly the same as that on the sprayer, but it does thread tight enough to hold securely. As others have mentioned, you don't want to be putting that fitting on and off too many times, but the way I see it is once you get the thing assembled it should stay that way for good.
As for the size of the sprayer, 56 ounces is big enough to handle a lot of line. Eg: six feet of 3/16" ID beer line holds a mere 2 ounces of fluid. So this little dude even just barely loaded will hold enough BLC to fill my six lines and faucets, and after letting that sit for awhile, will hold enough water to give each line a good flush.
So once again I'm quite happy to be following someone's footsteps on a great idea presented on HBT! (that's becoming a habit
And I can now free the ball lock keg I've always reserved for cleaning duty to a more noble use - holding beer!
Cheers - and thanks!
[edit: I kept thinking that 1.1 oz/72 inches of 3/16" ID beer line couldn't be right, so I just double-checked my math and the real value is actually 1.988 ounces. Still pretty small volume that suits this rig perfectly for at least 6 lines. Cheers!]