Slow Cooker

• Use lots of water. Maybe more is lost to evaporation over the long cook times or something?
• The cooking may need longer as the temperatures may be lower, even when the slow cooker is set to "high" or whatever knobs they give you. Also a glass lid may not create as much internal pressure as from a heavier pot on a stove.
• Perhaps pre-soak beans as especially the "have sat on shelf for who knows how long" variety are very dry and otherwise take forever to cook. This can be done like 12 or more hours in advance with plenty of water and enough salt to prohibit the bad bacteria. Like maybe 2% salt by weight of beans.
• On an unrelated note, some beans like to "crack" overnight as they soak so keep the slow cooker away from the bed if you are a light sleeper.
• Maybe do not mix the rice in early, as that needs less or no pre-soaking compared to the beans, unless you do want rice goo.
• Mix things up! Try beans with rice instead of rice with beans.
• Keep oils out of the cooker if possible as that complicates cleanup. Olive oil could be added when serving to the bowl, not to the cooker. Or if a good scrub is going to happen, try making a sauce after removing most of the materials?