This is interesting. I'm always willing to try some zany stuff. Got a link to the kind of bucket based exercises you were doing?
This video pretty much covers all the exercises and can be used as a follow-along (although I don't do so many exercises, but good to try them to see what feels good):
I try to make sure I am going for a good intensity, I will often break out in a sweat and even maybe a little endurance grunt as I get pumped and push on, especially in the last exercise. At the moment I will typically do the following:
1. closed fist rotations (called wax off in this video)... 25ish reps
2. closed fist rotations the other way (wax on... if you please)... 25ish
3. closed fist flappy things (called paint the fence in this video)... 25ish
4. closed fist flapyy things (potato masher in the vid... but I turn my fists so my knuckles are facing towards each other then flap kinda up and down/forwards and backwards)... 25
5. Finally this full hand grip and open movement, just think about spreading your fingers/hand as wide open as possible inside the rice and then gripping into a fist then boshing back open to fully extended aggressively... you can get a good rhythm with this one... 50 reps
That's usually it. Brush the rice off, walk around, maybe do another round, or a few more. Adjust the reps for yourself. Maybe start with just 10 reps for each. With the fist rotations try to make sure your wrist is staying somewhat still and the fist is going round in the rice, which for me means engaging my shoulders and core, rather than rotating the wrist around the fist which stays relatively static in the rice, which is much easier.
For me this is a great warm up for fingerboarding or grip training. If I have done a fingerboard workout or been climbing I will add this finger clawing movement where I put my hands in fully open/extended and then just flex the first two finger joints, so not closing the whole fist but just closing the fingers (think comedy martial arts tiger claw). This (especially the opening movement) works some deep extensor that I feel very intensely and makes my fingers feel super buttery after cranking on them. The thumb-specific ones in the video (eg. crab claw) also feel great, its so weird to get pumped in the thumb flexors, and I'm sure that the rice bucket in general has made my pinch/thumb strength much better.
Play around with reps or whatever, but for me it is important to do it somewhat aggressively so you start to get a bit fatigued by the end of each set, before switching exercise. In the beginning you might get DOMS in some weird places (I did, like in the sides of my fingers and in my palm, and very intensively on the forearm extensors).