Cheers @JB_Winnipeg. It is still hit & miss and a work in progress on the lower strings, but definitely smoother - its feels like when I’m warmed up, but its accessible almost straight away.
It was almost impossible to do the version of the knocking motion that I did with the pen/credit card, but it seems to have shown me what a knocking motion actually is - it looked more like forearm rotation to me at first - I didn’t see the flexion/extension.
If I was to sum it up, I’m feeling the knocking motion on the upstroke. I only need to add a tiny amount when I get it right, which is good considering the below
Problem to fix is on the lower strings, where the slightly different position of my ring and pinky affect my ability to knock. I tested it on the table too - if I hold out my pinky and try to knock, I can barely knock at all! On the guitar a similar problem occurs when I try and lift my middle, ring and pinky up out of the way of the strings.
That aside, I’m pretty pleased with less than an hour’s work!