It's quite common to migrate databases between staging, testing and production environments for Rails Apps. And
heroku db:pull/push is painfully slow. The best way I have found so far is using Heroku PG Backups add-on and it's free. I followed following steps to migrate production database to staging server:
1) add pgbackups add-on to production and staging apps
heroku addons:add pgbackups:basic --app production-app
heroku addons:add pgbackups:basic --app staging-app
Since I am only using pgbackups for migration, basic plan is enough for this.