Dirk realized as soon as he noticed Dave couldn't speak that there would be some trouble here.

"Slow down, chatterbug," he teases in his usual monotonous cadence. "You just talk a mile a minute, don't you? I can't keep up." And then he glances over his shoulder. "You can sign at me. I've been reading up."

Okay, he's still a beginner. But he at least wants to try understanding.