I agree. Soak them in water for a few days first, then Dremel tool them is easiest. I have also used an die grinder with a cut-off wheel on dry pots.
One reminder on using pots, if there are drain holes or the like in the pot either enlarge it to a size to allow adult animals to pass through easily, or plug it up. Your caudates can get stuck in these holes otherwise and drown or get lacerated severely.