same thing you're going through now, Tamarack. I recently bought both a Switch Rod and a Decho 7wt, and have been practicing and learning a lot in the last couple months.
I don't know anyone where I live in Minnesota that Spey casts, so I've been going solo. Undoubtedly getting individual lessons is the best approach, if it's an option for you.
I don't know what advice others might give you, but for myself, I learned the most by purchasing Ed Ward's Skagit Master DVD, and watching it a bunch of times, and practicing both on the grass and in the water (fishing for smallies).
I also watched Mel Kreiger The Essence of Fly Casting 2, and Rio
's 3 dvd set on Spey fishing. Both are great and helpful. Plus the great books by Dec H and Simon G. Plus all the chatter on this site -- amazingly helpful, and nearly every conceivable issue has been addressed and is archived. Plus you can find stuff on Youtube. I had to figure out, however, that I couldn't mix casting approaches as I'm learning. So I settled on Skagit style and have attempted to learn the basics. And for that, the Skagit Master dvd has been absolutely invaluable. I recommend it. (Apparently Vol 2 is out, or soon to be out.)
He covers super basic principles for sustained anchor casting (pick up, set, sweep, 45 thrust, etc). Once you learn those they can be applied in all the casts. He goes over just a few basic casts that are foundational (C-Spey, Double Spey, Perry Poke, etc). Thanks to EW for the clear and informative teaching, and for breaking the cast down into the component parts.
The learning curve is steep, especially if you have muscle memory for the single handed style, as I do. But it's coming along nicely. My casts are improving, and occasionally it all comes together. Feels pretty dang good too.
Good luck. I hope this helps.