Once a batch of beans have been cooked, just let the ones for the freezer cool down. Bag up and leave in the fridge to chill prior to freezing.
Usually we'd take out of the freezer a few hours before using so they'd be mainly defrosted but I suppose you could add still frozen to a stew.
Extra cooking depends on what bean, what you're cooking etc.
We don't use the pressure cooker as much as I would - Val's never quite forgotten her Dad making a stew when she was a child, overfilling the cooker and redecorating the kitchen ceiling through the safety valve!
Cara has one of the more modern multi-cookers that pressure cook, slow cook, make yoghurt and probably fixes a coffee too. Personally I prefer our analogue technology old pressure cooker, nowt to go wrong
Incidentally, best book ever written on beans is
The Bean Book by Rose Elliott One of those books that you replace because it gets used so often.