Antonius,
The horseradish mayo is available at local Butera stores. The closest ones to the city are either in Norridge on 4411 N Cumberalnd or 4761 Nagle in Harwood Heights. Not a bad local chain for various ethnic (Mexican, Italian, Polish) specialties in the burbs with typically pretty low prices. Kind of a low rent Caputos if you get my drift. Steer clear of the seafood.
The chicken breasts: I brined overnight in salt, brown sugar, garlic powder, onion powder, and then rinsed and then coated with mustard, brown sugar, ginger, and s&p. They cook quick on the smoker.
For the beef I was kinda of trying to duplicate the beef on weck of Buffalo, but didn't have the forthought to have my wife bake the rolls with the standard salt and caraway.
tony g