Spoon the oil into a large (10-inch) skillet and set over medium heat. When hot, add the arbol chile pieces and stir until fragrant, about 30 seconds. Add the beans and use an old-fashioned potato masher or the back of a large spoon to mash the beans into a coarse puree. Stir in the garlic solids and simmer briskly until thickened to the consistency of soft mashed potatoes. Taste and season with salt, usually a generous teaspoon, depending on the saltiness of the canned beans. The beans are ready to serve.
NOTE: the beans will thicken as they sit and cool off, so if not serving right away you’ll likely need to add a little water to get them back to the soft-mashed-potato consistency.