If you’re using the paxolin/superglue method, simply saw through the paxolin (carefully) any superglue left will be ground away. If you use epoxy, and I only use it to dop for the crown cutting, use a cone dop with some blutac in the bottom as epoxy will rip the culet off when removing it. To remove the epoxy, soak in dichloromethane. Not the most pleasant stuff but is ok if you are sensible. This turns the epoxy into something resembling rubbery cheese if left overnight or longer. Let the stone pop out by itself or the stone will be ripped. Clean with acetone first and then isopropyl alcohol. Dicholormethane can be found in some paint strippers or can be purchased by reputable sellers.