Hi Harjot,
In 5.2 we merge the current implementation for Variable Persistence with the core marshaling mechanisms of drools.
You can find a test that show how to configure the new Persisters in the following test inside the jbpm-persistence-jpa project:
https://github.com/droolsjbpm/jbpm/blob/master/jbpm-persistence-jpa/src/test/java/org/jbpm/persistence/session/VariablePersistenceStrategyTest.java
I was responsible for that merge and for the unification of these mechanisms, so please feel free to report any problem that you have with it.
Greetings.