Below you find my route suggestions. It's all depending on your time you want to take for this trip and the weather. Most of the route goes a bit parallel with the motorway heading from Belgium to Switzerland. So if the weather turns nasty you can easily pick up the motorway. This route is for 75% small scenic roads the other 25% you need to accept as feeder route.
Motorway to Namur ( south of Brussels) Heading south via E111 to Dinant. Follow river to Givet and Revin Follow river to Bouillon and via Herbeumont to Florenville Via Virton to Longuyon towards Metz Via Metz to Chateau Salins To Lorquin Via Col de Donon to Schirmeck Via Champ du Feu to Provenchères and Ste Marie aux Mines Via Col de Baganelles towards Col de Calvaire Turn right "Route des Crétes" towards Grand Ballon After Grand Ballon via Thann to Masevaux Turn right to Ballon d'Alsace At the Ballon take route Belfort After Belfort to St Hippolyte Via St Ursanne and the Corniche du Jura to Glovelier Towards Tavannes and later Biel Via Aarberg to Bern Via the motorway to Interlaken and Grindelwald
The best is you use the Michelin maps 53-56-57-62-66-70 to find this small detailed roads.
For a tour like this I search for this little scenic roads on the maps, make the route on my computer via Base Camp and after I did this, I load it on my Garmin 660 or 550. This makes it very relaxed to drive and you don't have to look on the maps during the tour.
