You normally would save the *USRPRFs using SAVSECDTA or the QSRSAVO API and then restore the profiles using RSTUSRPRF. This would generally be a one time effort.
To keep the profiles in synch across the partitions you can use various APIs and exits which allow you to know when a profile has changed (or a new one created) and then propogate the changes to one or more other system/partitions. The Security related APIs and exits can be found here and the Save Object API here. The book APIs at Work Second Edition (which I do have a financial interest in) also discusses this very scenario in Chapter 12 – Security APIs.
Another possible way to keep the profiles synchronized is with Management Central.