Hi Zach,
The Switch cast is nothing else than a Single Spey cast without change of direction (actually the Single Spey cast is a Switch cast WITH change of direction). You can also view the Switch cast as an accelerated or dynamic Roll cast, where you lift the line that is in front of you out of the water, anchor the leader in front of you, the “D” loop gets formed, and then you perform your forward stroke. The Switch cast works fine with single and double handed rods.
The Switch cast is also nicely described in the DVD “RIO’s Modern Spey Casting” with Simon Gawesworth and others (Chapter 7 of Disc 1).
I recently started practicing the Switch cast and it is a lot of fun. I use a Guideline Pounch Pro line and it works particularly well for Switch casting since it has a long belly with lots of weight in the front part of the line.
Cheers,
Jean-Paul