Strong voice, I don't know. My voice has always been really weak. But sounding natural, yeah, most probably. For one, I think you should try to speak in a feminine matter all the time, not just when you go out. It'll make your practice much more effective. Also, singing, even if it's hard, even if it sounds horrible in the beginning, can help a lot. By working on really hard things like songs, you'll make yourself better at easier things like speaking. A bit like a hockey player will lift really heavy weights to be better at manipulating their light hockey stick and puck.