I need a technique that I am obviously lacking.  I'm working on some 10-12 inch wide plates and bowls where the bottom of the inside should be flat, truly flat.  Past eyeballing with a ruler across the plate or inside of the bowl, and using a small squared scraper, I put on some mineral spirits to see how the sanding works before putting on a real finish. Looks pretty good to me, but  I still seem to get waves that show up when putting a finish on with any kind of shine.  
 
	My best shot is to just sand the daylights out of the piece with a piece of sandpaper on a wood block to smooth out any waves that circle the center.  Is there a faster, simpler, better way?   
 
	 
 
	Thanks, as always.