A nice program that is commonly used here is Praat. I didn't do any training or anything I just used the program to record my voice and listened to the playback. It also allows you to see the average frequency at which you are speaking. I practiced on it by recording myself reading a page in a book or magazine, or practicing like I was about to interview, or pretending I had a youtube channel giving updates, or would just ramble on. By doing this I get identified on the phone as Maam/Miss/Mrs 98% of the time even if I say my name is Josh (still getting ready for legal name change). This took time and evolved over about 4-6 months. I think you'll know when you sound feminine. I just sort of went, "huh, that sounds about right" and continued to use that voice.
Sorry if I rambled on a bit there.
