If you want to audit your entities changes you can consider to use the project Envers. This project makes easy the audit process on entities state with just only straightforward annotations. I tried it out and it's good.
Looks very interesting ...
But I doubt it can help with SMPC in manual flush mode. I should investigate this.
You can get ideas on how this can be done with either hibernate interceptor approach where you log full change in a separate audit table.
Or you can look at EJB3 listeners to update create tstamp and update tstamps on your entity.
I think create-onflush and merge are probably the events you are looking for for create and update respectively. On 2nd thought you can probably achieve create/update tstamps logic in a regular Hibernate interceptor, the choice is yours.
Thanks for your help, I think that may be what I was looking for. I'm going to investigate about that and see if that fits what I want to do.