I used this super easy and effective dutch routing app, Fietsknoop
I don't have a dedicated GPS , so at first used my phone, but I'm not keen on having my phone on a handlebar mount or having it on all the time, so I ended up just writing down the days routes "junction post numbers" on paper to follow the Fietsknoop suggested days route.
Looked at phone the times we missed a junction or just wanted to see exactly where we were.
Used it a bit also in Eastern Belgium, but don't know how far it extends