Singing in the move you will have to pay just as much attention to your face as anything. And if still shots are taken while singing, you'd be suprised at the faces that come out LOL! Don't hold your breath (unless there are advanced pole moves that call for it, I wouldn't know...) Usually when I am doing something difficult, I let the face ride for a while, and when its time to work on that part of things, I get an audience, even if its only a friend or my hubby (someone who understands dance and what you do. If you have a friend that doesn't get it, don't ask her lol, you'll most likely get "That looks good. That looks good too. That's fine" because they aren't sure what to say)
So audience there, do the move, let the face fall where it may.
Then do the move, with the biggest cheerleader smile you can muster.
Then do it with an overly exaggerated almost comical sexy pucker.
Ask for feedback. Record practice so YOU can give yourself feedback. Maybe your sexiest face needs to be "over the topped" a little to come through on stage. Have someone take random photos as you do your routine, and you can feel around for the funky faces. FEEL the emotion/mode/expression you want on your face. If you're playful, use that. If you're all about drippin' sexy, use that too. Drama or burlesque is REALLY helpful when it comes to dancing and faces. That being said, I am a beginner poler, but I've been a dancer/actress/singer forever it seems. I know NOTHING about pole competition or what is expected of a face in that arena. I seem to always look either really excited when pole dancing, or really mournful lol. On days I'm doing good, I look PISSED lol no matter how happy I feel, its pure fury on my face. Good luck!