My new Seiko SKX031 is running a little fast, and I want to take off the caseback and slow it down. How can I take off the back without damaging it? I know that there are special tools to do it, but I don't want to have to buy something and I don't want to take it to a watchmaker, as it will probably take much trial and error to adjust the speed. Also, can someone please tell me what would be best for adjusting the movement? I was thinking a small flathead screwdriver.