Keep your eyebrows up when you ask the question — that action tells everyone that you don't expect an answer. And if you're on the receiving end of a rhetorical question, you'll recognize it because the signer will barely pause before answering his own question. His hands won't go down to give you a chance to put your hands up to respond.
When you ask a rhetorical question, you use who, what, why, where, when, and how to make the sentence rhetorical, but you don't add a question mark because you aren't really asking a question. You are setting up the question to answer it yourself.
English: Brent is on my team.Sign: MY TEAM-- WHO — B-R-E-N-T
English: The tournament is in Pueblo.
Sign: TOURNAMENT WHERE — P-U-E-B-L-O