If you go through the Netherlands or Belgium, there is a program you can use called Vrinden op de Fiets (may be misspelled). Costs 10EUR a year to join, then gives you access to a large number of hosts along the cycle network who will accommodate you in anything from spare rooms to houseboats to second homes for a flat rate of 19EUR a nite a person. They operate in other countries as well, to a much smaller extent, they may have German hosts.
As far as the camping, IMO there is really no way to responsibly make a campfire wild camping, you will always leave a trace.