Establish external database connection in production on Heroku

I am trying to establish a connection to a secondary, external database on Heroku (this is a PostgreSQL db running on AWS). I am trying to find the easiest and/or best way to do this.

I have tried using a Capistrano task to copy the database.yml file during deployment to Heroku:

after "deploy:update_code","deploy:config_symlink"

namespace :deploy do

  task :config_symlink do
    run "cp #{shared_path}/shared/config/database.yml #{release_path}/config/database.yml"
  end
end

I have tried establishing the connection via Heroku config vars:

class Pgdb < ActiveRecord::Base.establish_connection(
    :adapter => ENV['PG_ADAPTER'],
    :database => ENV['PG_DB'],
    :username => ENV['PG_USER'],
    :password => ENV['PG_PW'],
    :host => ENV['PG_HOST']
  )

  self.abstract_class = true
  self.table_name = 'test'

  def self.getCardInfo(card_name)
    get = connection.query("SELECT * FROM test)
    get
  end
end

I can't find any documentation that makes sense or tells me exactly how to do this. I do not know if I'm close or way off in the attempts above. I'm looking for any solution that fixes the above attempts or any other solution to this problem.