I use green painters tape on the lenses, then put ductape a 1/2" wider overtop, comes off easy, you get some residue, but varsol/kerosene fixes that. Electrical tape will take longer, but if your worried about residue it is easier. don't forget to unplug your lights/take out the fuse (depending on your bike), make sure your front brake pads are in good condition (I recommend bringing a spare set if you do this regularily), also check what your tire manufacturer recommends for the track (you'll run lower psi at the track than on the street usually).
last thing, when you don't think you'll make a corner, you will, lean more. Your tires have more grip than you think. Easy to say, hard to do in a panic situation. If you do go off into the grass, rear brake only, don't use your front.
