I ordered the bark online and they pieces are a fairly uniform 1/2 inch or so in size.
I read somewhere that you can judge whether the pot needs watering by feeling the weight when you pick it up but that's never worked for me because the potting mix is so light. I tried a hygrometer and that tells me that the pot is dry a couple of days after soaking.
Soaking for an hour once a week seems to work. I do soak them for longer during the summer.