Google is useful but misses a lot. Gravelmap is very promising but super limited right now (I'm adding stuff regularly, and hope it takes off). Strava route creation is also promising but a near total failure at the moment (it doesn't know about road surface type and won't route through visible intersections half of the time).
Caltopo and Locus are the pro tools right now (AFAIK).
Check out multiple map overlays to find different roads. Verify with satellite view. Double verify with Earth so you can check angles.
I created this route on Locus from my RV and rode it yesterday. It was awesome.
https://strava.app.link/zXMaxJiyIeb