SumikoKeel, have you tried a walking foot with your multiple layers? And I assume you know you want to use the appropriate needle for denim? When working with flannels, I remove throat plate and clean that area and bobbin case area very frequently, like every other bobbin change because flannel is so linty. Not trying to talk you out of an older machine, just throwing out these coping mechanisms til you find the right one for the right price.