When I cook certain foods on my cookie sheet they leave a sticky residue on them that doesn't come off after soaking in hot sudsy water and/or scrubbing with a heavy duty Ocello pad. The only thing I've found that gets it off is a SOS pad. But aren't those bad for the non-stick finish? My cookie sheets look gross because I can never get them totally clean! I just made a pizza and the instructions said to put 2 tbsp of vegetable oil on the pan, then set the pizza on top of it. Well the vegetable oil is stuck on there! It feels like a sticker was there and the sticky stuff is still left. Any suggestions?