While walking backwards, keep the arms extended but pull your shoulder bladed together. Take small steps and drive backwards with a smooth and continuous stride. Lean back as much as you need to in order to develop enough balance and pull.
In the second variation, a higher weight may need to be used but extend the arms in front and drive forward. Lean as far as is needed forward to develop balance and purchase while moving. Attempt to keep the arms in a strong stable position while moving by slightly externally rotating the shoulder and squeezing the tops of the shoulder blades together.