If they are bad, save yourself the heartbreak and get a new tank. I have tried the buffing method and it does not work unless you have very light scratches. You can rent a buffer for $10 and the cirium oxide compound is only $6 a pound and is far more than you will ever need. So, as you can see, it is not expensive. I tried no less than 10 diff types of glass shops in my area and NONE of them wanted to take the time to work on it. Let me put it to you this way - I worked 3 days, 6 -8 hrs a day on mine and have decided to swap out the tanks in the spring!
keith