Note if you’re migrating away from Heroku, you can’t use pg_dump on the server directly, so you’ll probably want to pg:pull your database to your local machine, and then follow the above directions from step 2.
You also will probably skip the commands related to uploaded files, since Heroku probably already forced you to use S3 for assets.
(Also, if for any reason you’re using pgbackup restore, be sure to pg:reset first or you might end up with a frankenschema like I did and your migrations won’t run.)