Are you driving or taking public transport? I recommend taking the TGV to Rennes and then the shuttle bus to MSM—it’s a lovely drive through the countryside, and someone else is doing the driving :)

If you want to avoid the expressways because you think they are difficult to drive, I found that they were very easy to drive. Like US Interstates or UK Motorways, only even faster! If you take the secondary routes, you can get messed up and take wrong turns going through all the towns.

If you want to avoid the expressways because it is more interesting and scenic on the smaller roads, then I agree with you. Just make sure you allow plenty of time or that you are on a flexible schedule.

We drove from Mont St Michel to Paris on secondary highways through Alençon and almost to Chartres, and it was VERY slow going. When we finally got on the A-11 we cruised VERY quickly. I was bummed because we could have visited Chartres cathedral if we had taken the quicker way but we had to get to Paris to get rid of the rental car and we had a hotel reservation and it was getting late.

So, it isn’t difficult to find a route without using the Autoroutes (the huge expressways). You might take the N176 to the N12, but allow an entire day to drive it, whereas getting on the Autoroutes (A84 to Rennes, then A81 to the A11) will get you there in less than half the time. Nothing wrong with taking your time, I think its the most rewarding way to travel. Just be realistic about your goals.

I recommend getting the yellow Michelin road maps that cover the area between M St M and Paris. I think you can do it with one or two maps and I found them at Barnes & Noble. They are very detailed.