I still know of groups in their informal little get togethers who use the old 90% of the difference method when playing 4BBB because they stubbornly believe that the old and new methods deliver exactly the same results in all cases.
We are looking at havng 3 boards. Go to board #1 to get your course handicap. Move along to board #2 to find the required % for the competition that you are playing. Finally use the % boards to find your playing handicap for the day. A little simple maths might then be required for matchplay before moving onto the tee to play golf.
I have printed off my clubs version of @BanchoryBuddha’s table and have it tucked in my scorecard holder. I never need to wonder or ask, and I can immediately resolve any disputes or disagreements over this stuff.