Domodossola is the Tours Starting Point
It's located at 1.30h from Milan(120km)and 2.00h from Turin (200km) and it's easy connected with highway and trains
Train is a very good solution because you have no stress and is cheaper.
Domodosola is on one of the main International Railroad, so there is a connections every hour.
More is lot more "Green Idea", something that in our days must be considered much more.
If you choose the Car solution, A8 Highway from Milan or A11 Highway from Turin
and continue with A26 in Gravellona Toce/Simplon direction