The evening before, sort and rinse the beans (sorting meanings taking out bad beans or debris in the beans) then place in a container that will fit in your fridge, add water to cover by 2 inches, cover and refrigerate over night.
Next morning, drain and rinse the beans and place in a large pot for the stove top, add water to cover by 2 inches, bring to a boil for 15 minutes, remove from heat, drain, rinse, and pour into the slow cooker, add enough water to cover by 2 inches (they will swell during this). IMPORTANT NOTE: kidney beans do have a toxin that needs to be removed by boiling first, a slow cooker will not come up to the temp needed to remove this toxin.
Cook on Low setting for 7-10 hours or High setting for 3-5 hours. The beans are cooked when you can mush them by simply pushing against the roof of your mouth with your tongue. Last thing you want is a crunchy bean, that is not good.
When the beans are done, drain the water from the slow cooker pot (carefully!). Rinse the beans and return them to the pot, add BBQ sauce of your choice and the hot dogs or sausage. I would cut the hot dogs to about ¾ inch pieces, for the sausage, since it is a larger diameter, I would slice into ¼ to ½ inch pieces. Give this a quick stir and place on Low setting for 4 hours or high for 2 or 3 hours, at this point you are just heating everything through. Serve as a side dish, lunch (the day after, always better the next day), or for a filling main course with a salad on the side.
Serve and enjoy.