Since the stay in purgatory is connected to prior sin, it seems reasonable to say that "some kind of pain" is there. The Gospel mentions "the torturers" (Matthew 18:34), and so does Cyprian. We understand, of course, that it is a disembodied soul that is suffering, so any physical or physiological metaphor is just that, a metaphor.
Matthew 18:34 never struck me as describing the fate of someone who was headed for heaven.
I am not the person to interpret the Scripture, but this passage certainly suggests that it is God who sends us to a jailer and a tormentor until the debt is paid back.