Their episode 23, "Quassim Cassam discusses transcendental arguments," serves as a nice point of re-engagement with epistemology in light of our touching on that in our Sartre episode (and moreso in my Close Reading).
Sartre, following Heidegger and possibly Husserl, thinks that Descartes's skeptical challenge is a non-starter. We can't coherently doubt the existence of the external world because we're already always engaged with it: consciousness (or in Heidegger's case "care," though I recall at least one listener objecting to my analogizing between the two terms) has is intentional: the "external" world is something we're directly in contact with (at least an aspect of it; the entirety of even an individual object is transcendent).
In this very clear and well-conducted Elucidations interview, Cassam talks a bit about an analytic version of this response, which is one given by G.E. Moore in (among other places) his essay "A Defense of Common Sense." In short, it's a matter of epistemic priority. Moore and Sartre say we have to start philosophy with what we know, which includes things like "there is a hand in front of me." The task becomes figuring how what this claim really means and how knowledge must work such that we can and do know it, and by extension how we might in some circumstances be wrong about this sort of claim (such as when on drugs or dreaming) but yet we are in general, correct about this. To the skeptic, starting at this point utterly begs the question, but for Sartre, at least, to even ask the skeptical question requires abstracting from the concrete situation of knowledge as something like self-evident presentedness to imagine some greater kind of knowledge which, it turns out, we just don't have.
The interview is frustratingly short, of course, but very thought provoking. In the wake of our Sartre recording, I'd suggested to my fellows that we do a little epistemological review episode with some Berkeley on idealism and then Kant's and Moore's attempts to refute it. If you second this suggestion (or contrarily think it would be boring), speak up!
Note that Elucidations has now added a blog giving some additional episode description and follow-up (though not on the Cassam interview).