How to migrate old uploads to S3?

I now have all new uploads going straight to S3 but now I’d like to move all previous uploads to S3 as well. Is there a How To for this?

I searched the forums and found bits and pieces but not a step by step guide. I was unable to figure it out so far.

You should be able to use the uploads:migrate_to_s3 rake command. This would migrate your local files to the configured S3 bucket.