Hole saw like this one:
http://www.homedepot.com/webapp/wcs/...cStoreNum=8125
It will cut about 2" deep.
Just need to get one that is the width you want the cut out. Make multiple cuts until you get the length.
The correct name I guess is "Compound Slide Table". I seen one at my local harbor freight last time I was there. Dremel is probably cheaper.
http://search.ebay.com/compound-slid...fsooZ1QQfsopZ3 If you get one of those then you can just cut the plexi with a endmill instead of hole saw.
If the copper is that rough start with some heavy grit and work your way to higher grits. Here is a guide form someone that forgot more about the subject then I will ever know:
http://www.leesspace.com/Lapping.htm