Get the relevant Jeppesen VFR charts for the area(s) you want to fly through and plan a route that way there are plenty of smaller airfields certainly in germany. I flew from Holland to eastern Poland this summer and had no problems.
As for landing off airfield in Holland: you have to get permission from the property owner AND permission from the counsel of the area where you land this all in writing ofcourse.
Then at least 24hrs before the proposed flight you need to fax the dutch CAA and Aviation police with your details.
There are also various heliports within Holland you possibly could use as well.
Safe Flying
