@GmanG certainly not bad to learn sharps and flats (although I’ve never had someone give me those hand signals. 
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Great point about adding sharps each position to the right, and adding flats each position to the left, and I’ll add: that’s why when using a C harmonica to play in the key of F, what’s often referred to as “12th position”, I know pro players like Carlos Del Junco and Joe Filisko will call that 1st flat position, and the playing in the key of Bb on a C harmonica is 2nd flat position, etc…