I find that a strong spray of the pad with the garden hose (jet nozzle) right after I use them gets all the product off. Then I put em back on the UDM for a quick spin dry.
If they are especially gunky or dirty, I soak them in a dish detergent solution (usually Sunlight) for a bit.
Dawn Power Dissolver cant be beat. Its less then $3 at walmart and has removed stains from my microfiber towels that even a normal wash couldn't remove.