Miku isn't going to make your manly voice girly, it's a sound source in and of itself. Like a vocal rompler really.
Here's a fun idea, sing twinkle twinkle little star (or something equally simple) in different octaves/transpositions and styles until you nail the range and placement that can be pitch-shifted into ladiesville with least effort. I recommend trying some MAJOR FALSETTO
I found that if I sit around the bottom half-octave of my range, I can pitch shift -5 and suddenly become Ultimate Manguy McDudeMale. Especially if I'm doing the yawn-voice open larynx thing. NOW GO FORTH AND GENDERBEND
Manguy McDudeMale!! :'D :badger:
But you really gave me inspiration, have to try that too.