I've read a hundred posts about feminizing your voice, but this one seemed to simple to work.
I googled "how to talk with a girlie voice".
So, first you pick a female singer with a breathier style. I chose Judy Collins. Listen to a couple of albums.
Next you push the sides of the middle of your tongue up against your upper teeth.
Then speak, but try to sing a bit, with an upward lilt or lift at the end of the phrase, not quite like asking a question but close.
Looking in the mirror and greet yourself as in: "Well hello there Ophelia".
Spend increasingly longer times talking to in this new voice, still imagining that singer you chose.
I do it in the car going here and there.
Soon you'll have trouble falling back into guy voice.
It works for me.