Hey there, Mike. My Extra Durable Magic Erasers are ready to make any stuck on marks, gunk, or grime be permanently erased, so it'll be nothing but a memory. Just add some water (gently squeeze out excess) and hold the Eraser as flat as possible. Then, rub the dampened Eraser across what needs to be removed. Yes, the Eraser will wear down as you rub it away. There will be some residue left by the Eraser, similar to what occurs with a pencil eraser. The material wearing down ensures your marks are being permanently deleted. If you need more help, give me a call any Monday through Friday, from 9 AM to 6 PM, EST. Our number is 1 (800) 867-2532.