Some Software you may find helpful
Joinr (Android & iPhone) We have been told that several Porsche Clubs have used this app to create rally's and driving events and it has worked flawlessly by participants. We do not yet have a report from an Ambassador.
My Route (Android & iPhone) Designed for delivery services that need to plan their route. It's is still in development and has some bugs. Once you have you map correct, it works quite well and prompts you turn by turn. You can also print out a copy of the route plan. There is a one time fee or $39 to create your route. The developers are accessible. ~ Bernie, July 2020
Rallista (Android & iPhone) - Requires you to pay $2.99/month.
Google Maps