In Germany the way is marked with obvious Camino symbols, a yellow scallop shell symbol on blue ground, sometimes additional yellow arrows for direction. In my experience it is usually only marked for the direction of Santiago, although there are exceptions.
If you want to walk backwards, France might be the better option.
Regarding accommodation:
There is no albergue system in Germany. You can stay in pensions, hotels, youth hostels ("Jugendherberge") or camp grounds. You can also call the pastor of the local church to ask for places to stay, sometimes there are locals offering a bed for a small fee. The via regia seems to have a good network of locals offering beds for pilgrims for pilgrim friendly prices, but I have no personal experience with that.
Walking in Germany, you need either a lot of money (hotels, pensions), a lot of creativity (ask at churches, fire brigade, ask locals) ... or a tent.
In France it depends on where you walk. The GR65 from le Puy has a network of "Gîtes" which are a bit like albergues but smaller, more expensive and need pre-booking. On other routes it might be different.
Happy Camino planning!