Any Good Techniques To Buff Scratches Off A Slab?

I've had pretty amazing results removing significant scratches from plastic watch crystals using toothpaste. I now use a polish made especially for watch crystals, though. Didn't care for the minty fresh wristwatch odor.

I can't think of the name right now, but can find the tube if you want.

Another one of my antique tricks is Liquid Brasso. I've buffed old plastic watch crystals, polished Coca Cola porcelain signs, tin lithograph toys and many ( I feel so old saying this) many years ago when I was a paramedic, we polished our plastic light bar with Liquid Brasso too. It will NOT remove deep scratches but will buff out small scuffs and spider web appearances. I would not recommend using an electric buffer. Try by hand first. Clean cloth and not that old can of Brasso that belonged to your great grandfather.

I've never had to clean scratches off of a slab, but if I had to I would use a CD/DVD repair kit, used for removing scratches from CD's and DVD's and restoring them to playable condition. I bought my kit at Radio Shack, and I'm sure that it would be available at Walmart or any electronics store. The kit is simply two sandpapers (I'm guessing 600 and 1000 weight) along with a polishing compound and cloth. Basically you sand the scratches out by hand with the sandpapers, and buff and polish with the compound and cloth. I have used it not only for CD's and DVD's but also watch crystals and other plastic items and have had excellent results.