I do a vocal warmup every morning that my speech therapist provided me, but apart from that, I haven't been able to find a good youtube video or other warmup to do to talk slower, lower and with more resonance/downtalk.

I know its a conscious decision to talk this way, but if I'm talking to a girl, all of these things just go out the window so I wanted to make it a natural part of my life. I started to simply talk slower and deeper with strangers throughout the day