Updating Access Rights tables in bulk

Hello,

We need to assign Accounts(and other related custom objects) to different groups(Organizational roles) based on a field in the Account object. The field is similar to the "Assignees Group" field in the "Case" object.

We need to do this in bulk for all the records after some data is imported. Is there a way to update the AccountAccessRights so that the access rights can be refreshed for all the Accounts at once? If there is an example somewhere we can refer to that would be helpful.

We have looked into the business process approach, but it is slow as it starts a new process for each record processed and we see thousands of backlogged processes in the system.

Thank you