Siz - yeah that's a cute trick shot, the railfirst spin-'er-in. Can be done at 90 degrees (though more than 90 degrees? Ooof. I'd have to see it. I know it works in theory).
Ever use some of these other holding tricks? Your mention of railfirst reminded me of them.
I'm feeling pedantic, brace yourself.
This one I first learned in the 99 critical shots but I thought it was a mistake in the diagram. Ray showed how center left, high left, and finally low left would cause the cue ball to increasingly spin further sideways off the short rail. I was like "why would low left spin further than high left? The draw is bringing it backwards. There's no reason drawing the ball would make it travel more forward."
What I realized years later is he's doing a soft low left shot. It's a draw-drag shot, so the draw totally dies before it even touches the ball. But the left spin you put on it stays. So the cue ball arrives with no topspin, just pure sidespin, which gets bigtime action off the rail. A little known aspect of inside english shots like this is that often pure center sidespin will get better action than high+sidespin. You'd think that if high makes it travel more 'forward' after contact, and if left does too, then high+left would have a really strong effect. But the effect, while good, is not as good as pure heavy left.
In the diagram, "A" is where you go with the draw-drag left, and "B" is where you go with with plain high left, or a center left shot that has been allowed to pick up forward roll since it was hit softly. Holding to "A" makes the 2 a lot easier.
The railfirst shot I was reminded of is sort of like the one below. It's hard to diagram the exact situation but I know it when I see it. Basically if you hit the ball first, you're ending up at B or worse. Holding with outside, which I usually want to do here, may not be good because you can bump the 3 or get stuck behind it or jacked up over it. But if you load up with tons of soft inside, you can hit the rail way before the ball and then spin sharply into it. If you hit the 1 fat enough after the rebound, the cue ball won't travel much... or at least not as much as it would hitting directly.
