I'm in the process of planning a 6-8 day bike tour and wanting to keep it on gravel roads as much as possible. I've done about 150 days of bike touring in the past on paved roads, and I'm done rolling the dice with my life now that apps are so addictive that drivers can't help scrolling while operating a moving vehicle.

Gravelmaps has been a huge help, so has google maps using street view to check for gravel or if necessary the width of the shoulder. Even on side roads that haven't been streetview'd you can still check it at intersections to see.

The planning is VERY time consuming though, lots of permutations of routes to get between 2 points when the goal is to stay off paved surfaces each with various tradeoffs. It would be VERY cool if gravelmap let you input a start and end point and gave you a best route suggestion. Or even if google let you select gravel only.