Jeff, I've used the mustard/pickle juice binder and like just using plain mustard, I couldn't really tell a difference between the two.
The mustard/pickle juice binder seems to be a Central Texas-style barbecue thing that Franklin Barbecue alumnus have talked about using.
In a 2013 Texas Monthly interview (
https://www.texasmonthly.com/bbq/interview-john-lewis-of-la-barbecue/#comments) with John Lewis (La Barbecue, now at Lewis Barbecue), John Lewis provided the following in the articles comments section:
"Try 8 parts coarse ground pepper, 3 parts Lawry's, 3 parts kosher salt, and one part granulated garlic. Rub it down with a
half and half mixture of hot dog mustard and pickle juice first before sprinkling the rub on."
The crew over at Goldee's Barbecue have stated about binders in their YouTube videos (
https://www.youtube.com/channel/UCeqpZLU1wpvdad2ibbrO6fw/videos), to "use anything liquid, hot sauce, water, etc...it doesn't really matter."
In the videos, they've used the following binders:
- water (on 56 briskets)
- mustard and "a little bit of pickle juice" (on brisket)
- 70/30 mixture of Worcestershire sauce and yellow mustard (on pork spareribs, pork butts)
- yellow mustard (on beef ribs)
- 80/20 mixture of water and honey (on beef ribs)
- pickled jalapeño juice (on brisket)
I think that from a restaurant perspective, it makes economic sense to use whatever is on-hand (leftover pickle juice). Also, from that same perspective is to be consistent with the product, in this case the visual appearance of the brisket when finished.
Using mustard, Jonny White (aka Jirby) commented that "you want to make sure it (slather/binder) is nice and even...you don't want to see gloops of mustard, which can mess up your rub, making it gloopy."
Using the pickle juice to thin out the mustard makes it easier to apply the mustard binder to the brisket more evenly, making the finished appearance of all their briskets more uniform and consistent.