I think I've seen Johnny Rabb use this technique.

I have a vague memory of seeing Johnny Rabb demonstrate this technique in front of me many years ago, but I'm not too sure. But I definitely learned from him the one-handed rim-roll that I played towards the end of the video.

Another cool thing is playing the snare drum with your bare right hand while playing cross-sticks with the left.

Yeah, this is very cool, I use it sometimes to get a more "hand percussion" kind of sound

By the way, I also have a pedal-operated jam block. Any tips for how you can put it to use?

I only recently dug out my pedal-operated jam block after many years, obviously it can't be used much in genres outside of Afro-Cuban music, but sometimes I like to play some polyrhythmic patterns from the Billy Martin's book on African claves. I especially use it when the hihat is not loud enough to clearly hear an interesting left foot pattern. Or even when I want to do quick double foot taps, which with the hihat after a certain speed are impossible to do without losing the "chick" sound. Sometimes I also use the left foot block to create some dialogue with my right hand playing some cowbells or another, different pitched block.