My partner and I are doing exactly this in September this year! We have done some research, and the cheapest option so far seems to be purchasing the EuroRail Pass here in Aus, then using one of your travel days on the sleeper train from Amsterdam to Munich (we didn’t want to waste the 6 or 8 hours on train during the day). It leaves at 9pm from amsterdam. You need to reserve your seat in advance. Here is some info: http://www.eurail.com/eurail-hotel-city-nightline
I would highly recommend booking your accom beforehand - we booked ours a few weeks ago and it is already at astronomical prices!! Even the camping spots were filling up quick and charging ridiculous amounts! We ended up finding a hotel in one of the outer suburbs near a train station and will train into the main action! The suburb was called Unterhaching.