Try adding more ketchup or even water. You could also try not draining your beans and adding that liquid to the sauce. Don't really know what all the bean liquid is anyways, but if it can keep those beans moist in a can it probably can in a dish too!
I always save the water that the beans have been soaked in until they are done. If any moisture needs to be added, I use this. It doesn't cut down on the flavors of the other ingredients.
I like to add dark flavorful beer (like Guiness) to beans to help them from drying out and to add flavor.
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