First of all, if you want to use Spring Web Flow 2 the Spring 2.5.6 framework is required. Because Web Flow requires a base Spring infrastructure. The integration of Spring Web Flow inside a existing web application is possible. In this case you have to migrate the existing "flow" mechansimn to Web Flow, otherwise you can not use the advantages. In the book we show how to integrate with Spring MVC because its the best way to use Web Flow. In your case it depends on used controller framework / view mechansimn.
FYI: Conversation is one key element of web flow, therefore the maintance is done from the framework. The back button problem is solved by the framework, too.