BIDS Helper has a nice add-on utility "Aggregation Manager", but that is technically still BIDS.

SSMS has an "assign aggregation design" feature that assigns existing designs to other partitions.

http://technet.microsoft.com/en-us/library/ms181200.aspx

Once you do complete these actions, I think a ProcessIndex will save you some processing time. To my knowledge you would not need to fully reprocess the cube afterwards.