Anways, Here's our own Pete Coco showing us how it's done

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Hey diddy I just noticed the Bluegrass and Rockabilly thread and then your kind words above, thanks! I posted that video recently but it is a few years old. I will try and put some new ones up soon, maybe I'll do an instructional type slap video if anyone is interested. I've also thrown around the idea of writing a slap method book, but I've been really busy lately.
I find that higher action always works better for slapping, but there is a good middle ground you can achieve without making it too hard to play the bass pizz. It depends on each person and each instrument.
Also, I don't think there is one "Simandl" of slap bass methods. In other words, different slap methods seem to work equally as well depending on the individual. The way I slap is kind of an adaptation of Milt's technique, but I also don't have his sort of side-handed approach.
I think the best way to get better slap chops is to slowly develop muscle memory. To do this, take one slap pattern and meticulously practice it at slow tempos, gradually increasing it until it becomes automatic. Then, take a different rhythmic pattern and do the same thing. Then, combine them. Usually, I practice different rhythms with major or other scales, sometimes I just play over the form of a tune, slapping a solo-ish bass line.
Again, I don't think there is one surefire method, but I do think there are certain techniques and practice methods that can really help. They seem to work well with my students, anyways.
Pete
PS. This new Bluegrass and Rockabilly thread is an awesome idea!