Well, if you walk via Orleans you get to go past the grand chateaus, and I think a lot of the way is on a gravel bike path along the Loire that's pretty easy to follow. However, I haven't walked that route, so I don't have any personal input.
I wanted to visit Chartres again, so that's the way we went. This is about the least-walked route in France, I believe. When I walked two years ago, there was no information available in English except a very outdated guide from the CSJ, but I think they may have had an update since then. I used LePere, which is in French and very dreadful for this route, but it was pretty much the only print resource for the early stages. There is a very nice glossy booklet for the bicycle route (which is much longer) which is available in the tourist offices. It's in French, but it does have good maps and some accommodation suggestions.
I would suggest that in Paris you go to Compostelle 2000, which is the local pilgrims' association. They can help you with the best routes for getting out of Paris.
http://www.compostelle2000.org
Every
departement in France has its own pilgrim's association and their websites are your best bet for info on routes/traveling. Generally speaking the route roughly follows the GR655, but that loops around so much that you walk almost double the distance, so you'll probably want to look for suggestions about shortcuts. The Eure-et-Loir pilgrims' group has excellent information for that stretch and it's well-waymarked, too. They're a seriously nice group of folks and would help you with accommodations, too.
I broke a foot and cracked a rib and my humerus the second day out, so I had to go home from Cloyes-sur-le-Loir, but the stages I did were Paris->Vauhallan->Chevreuse->Rambouillet->Épernon->Chartres->La Bordiniere St. Loup->Bonneval->Chateaudun->Cloyes. Right after Cloyes you cross over into Cher-et-Loir and their association just says to follow the GR655, so you'll be more on your own at that point.
I would suggest you read through everything in the Tours sub-forum here, because there's a lot of info there.
I don't think you can do this route without relying on info in French, but google translate can help with that. The more French you know the better on this route; after Paris there just aren't that many people around and not a lot of them speak English, so I'd try to get at least some basic phrases in French. Everyone will appreciate your trying, no matter how much you butcher their beautiful language. If nothing else, be absolutely sure that you can hear the difference between
à droite (to the right) and
tout droit (straight ahead), because you're going to have to ask for directions sometimes. A simple, "
Chemin Compostelle?" and gestures will do it if you aren't too far off the route or where there's a crossroad.
Also, you will need to arrange for where you're going to stay the next day ahead of time most of the time. The area close to Paris is very popular for weekends and even the monasteries were booked up two months ahead of time when I was looking for places to stay. I was walking in September, which is, along with May, the most popular month for French walkers, so you do need to plan ahead.
But I loved it so much. I think about going back to pick up where I left off all the time.
ETA I forgot to say that your best friend for figuring out this route is IGN maps, especially the blue ones. They show all the footpaths. There is an app, iPhiGénie, which also has them, but I found that I couldn't see enough area on the small screen to easily figure out where I was going.