My opinion page addressing inquiries concerning clawhammer technique.
It's pretty much up to you but after teaching for the last 25 years I've come to the conclusion that you can get a consistently clearer sound with a "pull-off" instead of a "push-off", but that's only my opinion. I also believe it leaves your left hand in a better position to finger subsequent notes.
I like to think of the "pull" as a "pluck" and have my students visualize it this way.

Thanks... Mike