Czech Austrian Railpass

I%26#39;m considering getting a Czech-Austrian railpass, and have some questions:

My first trip on it would be from Dresden to Prague. How do I get it validated?

Am I able to do so in Dresden? Or do I have to get it validated at the border? Or can I get its first validation on the train?

If using it from Salzburg to Munich is it good only to the border, then I pay from the burder to Munich?

Is use of the Czedh Austrian railpass the most const-effective for the following rail journey?

1. Deutsche Bahn from Dresdne to the border, thence CA Railpass to Progue

2. CA Railpass Prague to Vienna

3. CA Railpass Vienna to Salzburg

4. CA Railpass Salzburg to border, thence Deutsche Bahn to Munich

5. Deutsche Bahn Munich to Cochen

6. Deutsche Bahn Cochem to Frankfurt Airoprt

An alternative I suspect would be a Eurail Selectpass and pay cash to the Czech portions

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It seems like the longest distances you are going to travel are within Germany. It would make sense to buy a German railpass (is there one with Austria?) and pay for the Czech portions of your travels. Czech and in general Eastern European railway tickets are usualy much cheaper than the German and Austrian ones. Plus, Germany is a much bigger country than Austria and Czech Republic, so normal tickets within Germany would cost you (assuming similar km tariff) more than the others.