For my birthday, my wife surprised me with this Swaty, which seems in very good condition. Very smooth, on the front just a chip in the lower right corner. On the back 2 corner chips (small) and some discoloration. I know NOTHING about them. How can I tell if oil has been used on it? What should I do to prep it? How do you use it...with water? All the usual newby questions, if you'll indulge me.