Well, you're not alone finding trouble when loading 120 film into a modern spiral. I've developed hundreds of 35mm films over the years with few problems during the loading phase, and I know and practise all the procedures advised above.

I started with 120 in the 1950s (without the benefit of Paterson's steel balls or other gizmos) and had few problems then, so what's changed? I think it's the move to allow spirals to take the longer 220 film or two 120 films, one after the other. This has lessened the gap between the grooves in the spiral, and I think it's this which has made loading 120 films more difficult today than way back when.