Sorry, thought you was on about the copper and sand paper / abrasive materials do not make acrylic go cloudy. Used it loads of time and always smoothed it off with wet n' dry and then finalised with some fine wire wool.

Look in the case mod section for people who use plexi and they always file it down after cutting it.

Edit: but the stuff that his blocks are using is more brittle than anything I ever worked with, so who knows