Life is too short to mess around with old laps impregnated with unknown grit.
Buy new laps.
I know people that have now accumulated over a dozen old laps, because they were on a fixed income, and the laps were cheap. They have done nothing with them, it's too much of a hassle. Their decision not to spend money on proper gear literally paralyzed them. Years later and they're still trying to figure it out.
Go to
http://www.gemologyonline.com/Forum/phpBB2/index.php to decide which laps to buy.
Better yet, find a club in your area and see if anybody is cutting near you, and willing to give you a lesson and let you cut a stone. Faceting is extremely time consuming, and deeply tedious, it's not for everybody. Don't spend any more money until you've sat in front of a machine for ten or twenty hours.