One suggestion is to get the cable car from the Chamonix central area to the first level cable car station, thereby avoiding the long zig-zag uphill footpath to it. Then walk to the next cable car station, at the top turn left and hike towards Les Houche below. You will climb a short ladder further on, this tells you that you are on the right route, then just keep walking, mainly downhill. You will soon come to a Refuge, a great place for views, drinks, lunch and so on. I camped there the night, just to the rear of the building. Then carry on down and down until you reach Les Houche railway station. At the station, turn left along a footpath, to the left of the river, and stroll back to Chamonix. A good day out.
I'm sure you know but just in case, the French use horizontal red and white paint flashes on rocks, posts, trees, etc to indicate straight ahead on the Grande Rondonee footpath routes, e.g The Tour du Mont Blanc. Very effective and simple, really hard to get lost. If you need to turn left or right the paint flashes are right angled and if you see a painted cross across the flashes dont go that way. I walked across the Pyrenees following these flashes, hardly looked at a map in 50 days. Normal footpath signs are used when routes cross each other.