before you start the aging, crumple up the sheet, a that allows there to be some darker lines, which looks nicer. i usually then put it in a jelly roll pan and boil some very dark coffee, because it stains better. take a teaspoon and randomly pour on top of the paper. have fun! (:
For levelling, I suggest that you wrap the cake up in 1 layer of parchment paper and 2 layers of saran wrap, then put it in a freezer bag and stick it in the freezer for a few hours. when you take it out again, you can level it while it's still somewhat frozen (just let it sit out for about 10 minutes). This way you can mess with the cake as much as you want without it crumbling. Good luck!