TweakFactor has posted a Cooler Lapping Guide
To get started you'll need three or for pieces of wet/dry sand paper in grits of 320, 600, 1000 and if you can find a 2000. The first two you should be able to find easily at Home Depot or some other hardware store, the last two however are for fine finishing and you might have to find them at a hobby store or automotive retailer that carries car paint products (such as Canadian Tire). You'll also need to be near a sink or have a cup of water handy.Read more