hey, my suggestion would be to buy the Euro Rail pass from there itself! yes, i did it when I was going from Berlin to Amsterdam, I took a 3-way euro-rail pass, and got 5 cross-country travel. And it just takes 5 minutes at the ticketing counter, tell them your plan, and they assist you better..

Regarding buses, you can get a travel card seperately for these 3 countries from the bus itself i think, or near to or in the train stations, they have a ticketing booth i guess

hope that helps..good luck and bon bon voyage!