One way you can look at this is that there are sort of a few different options for “two way pickslanting”. Here’s a little overview of those options as I understand them right now.
There is the Antigravity / Pickslanting Primer method, where you use occasional forearm during string changes. You can watch those for descriptions of how the arm adjustments work. They’re still reasonably accurate.
Then you have the “no forearm at all” approach. The “Crosspicking with the Wrist” lesson is our best description of how to get those movements happening:
https://troygrady.com/channels/talking-the-code/crosspicking-with-the-wrist/
Of course we’re using bluegrass roll patterns in this lesson. But what happened in my case is that once I started getting good at this, I started using this motion for other types of phrases, like scale playing. And when I did that, the movement split in half, where I wasn’t making the complete curved motion all the time, but instead, making only the downstroke escape portion, or the upstroke escape portion, as necessary. In other words, it became two-way pickslanting. This is what it looks like when you do that:
So to get the “wrist only” approach to two-way pickslanting I would watch the crosspicking broadcast, and start with the roll patterns as I describe. Once you start to do those smoothly, you can try this approach on other kinds of phrases and see what it looks like. In my case, I didn’t have to specifically try split the motion in half. It happened as a result of trying to go faster. So that’s one approach you can try right now. Right now we have precisely one data point of someone where this worked - me! Hopefully over time we’ll get more insight into different ways to approach this.
At the other end of the spectrum you have the “forearm all the time” approach. Our last workshop with the very snazzy title of “Crosspicking With the Wrist And Forearm” is where we talk about that:
https://troygrady.com/channels/talking-the-code/crosspicking-with-the-wrist-and-forearm/
This is another crosspicking technique in the sense that you can use it to play continuous one-note-per-string arpeggios. But what is interesting here is that this is pretty much the same motion we describe in Antigravity and the Pickslanting Primer as the pickslanting motion, except now you’re doing it on every note. So it basically becomes your picking motion. The benefit of this is that you can use it to play any combination of notes per string. You’ll still have to work out those lines and learn all the combinations of string changes in order to play them cleanly, so it’s not really a “get out of jail free” card where you just fret anything and the picking hand magically follows. That doesn’t really exist. But at least in this approach, you’re using the same motion for all the notes so you don’t have to deal with mixing two different motions together and trying to make that smooth.
Just keep in mind that when most people use forearm motion, the use it together with the wrist. So in this broadcast, that’s the motion we’re talking about, and how to recognize what the movement looks like when it’s “more forearm”, and when it’s “more wrist”. These are very broad categories so it’s more about understanding the concept.
Finally, I wrote a blog post on this subject which outlines the history of our insights into “two-way pickslanting” and shows a few video examples:
https://troygrady.com/2018/07/16/what-is-two-way-pickslanting-and-how-does-it-work/
Let me know if that helps!