Your (push pull) method is fine, but it will be tough on 80#. (Much safer than step through)
A stringer is just a length of cord* with a loop in each end, just a bit longer than the bow... zero cost.
File and extra groove just above the top nock.
Lower stringer loop sits on top of the regular sting lower loop (or you can make another groove or enlarge the existing one). top stringer loop sits in the new mock grooves.
Tread on the middle of the stringer pull up on the grip with one hand and slide top loop along the limb into it's nock... bish bash boch, job done.
Del
* Even braided nylon cord is ok, as the bit of stretch doesn't matter