Something...

You rack your brain to think of something convincing to say, but fail to come up with anything. With nothing else to say, you sign the job application and watch Grillby as he takes the pen and application back. After giving the job application a quick once over, Grillby nods his head and offers to shake your hand. Despite your hesitance at shaking hands with someone who appears to be made of fire, you do it anyway. Grillby's hand feels just a bit warmer than what you expect a human's hand to feel like. It's also more solid than you were expecting, which confirms that those muscles you saw earlier aren't just for show.

After finishing your handshake, Grillby takes his rag and goes back to wiping down the counter. You don't think you're being dismissed, though it's hard to tell. You suppose you could tell Grillby you would like to start working right away, but you could also talk to one of the other patrons here, or even Grillby, in order to pass the time until it gets busier. You could even leave the pub and come back to work another time if you wanted to.