I have seen a fair amount of videos that show someone speaking female then lower down to their original male voice then back up to female. Well this is great as in I hear that it can be done I know that voice lessons are still in order.
In the mean time I have been working with a simple iPhone (PitchLab) app that was not made for this but does test you. Just recently I purchased a new Dell laptop with a webcam that included software called Webcam Central that allows me to see myself talking along with facial language which really helps me more so than the iPhone app.
So if you are transitioning you might consider finding PitchLab and/or work with a webcam to record yourself, play it back and learn from it.