This seems like a lot of trouble and hamburgers I make myself are always good but I might just try this chef's method sometimes. http://www.businessinsider.com/how-to-make-hamburger-patties-2015-6
If I had to make a burger for a Michelin four-star chef or face execution, I might do all that shit. But the people I make burgers for would never notice the difference between that and plain 80/20 ground beef hand-formed into a patty.
My burgers are 50/50 beef and bacon. I run the cheap, lean cuts and the bacon through the grinder. Add a shit load of blue cheese for the orgasmo effect. Hit em with a little mustard and smoke on the grill. paired with tecate off the ice and it's white boy day.
Then just buy some fresh ground meat and don't over cook them. It's not hard to make great burgers on the grill.
Hamburgers are meant to be cooked in their own juices. On a grill the fat drips down and often the result is a dry patty. Try cooking them in an iron skillet on the grill. They will cook in their own fat and you still get the smokey flavor
You can dry them out no matter how you cook them. The key is to seer the outside helping seal in the natural juices and then cook them until they are cooked in the middle but not hockey pucks.
i think most people do this better on a grill than in a pan or on a griddle. People seem tempted mash that patty down with the spatula and squeeze out the juices and that makes them dry even if they sear them well.