Don't struggle with anything else except TSP--Trisodium Phosphate. Can be found at good paint/hardware store. However, I have not found it at the "chains". If you can't find it, call a local woodworker and ask where they get it.
My husband and I just got finished stripping and refinishing a 2-story oak staircase. Believe me, you'll think this is a miracle worker. Just follow the directions on the box.1. Get 1 bucket for TSP. Dissolve 1/2 in two gallons water and rinse. Sometimes a rag is all that is necessary, although a soft brush may be needed for trouble areas. 2. Get second bucket for warm water .The second step is rinse with clean rag. It works like a charm!