Oh, you have an Android phone? Hmmm, if you're not using it for anything else (like GPS), then I'd recommend trying it. I've dictated a few texts while driving (very few). And this was on an old $10 refurb Tracfone.

I think dictation requires data to function well, but I'm not sure. Just open a blank Gdoc before you start the car.

Have you ever tried Google Assistant? I have; I tried to train it to open Google Maps and find directions to my home whenever I said, "Chart a course home" (Star Trek style). Instead, it took me to Home Depot, and I didn't realize it until about 1/3 of the way into the trip!