Karenwong,
I'm out everyday as Teresa and have never had voice training , I feel it really doesn't make that much difference . The visual aspect comes before that if you look right (pass ?) you are over half way there , closer up if the makeup is well applied but not OTT finally when you speak the assessment has been made you are either accepted or not . If you then open your mouth and a squeaky voice comes out it could do more damage than sticking to normal . Besides it's not sustainable , it's possibly impossible to keep it up for more than a few minutes , I spend all day with my art group chatting away and on one occasion talked to a full lecture theatre for sometime about my TG situation , they didn't expect an altered voice .