Here's 2 lapping guides I found:
Lapping Guide #1
Lapping Guide #2
Now, there are some discussions on 1 of those guides as to how far you should go when lapping. Some say that it's best not to go for a 'shiny' finish (2000 grade for example) and just lap up to 600-800 grade. The important thing is to get the surface
flat . However, I don't want to get involved in that discussion as I am not an expert in this area.
The most important thing is to have a flat surface to work on. Glass is the preferred surface, but a marble work surface should be just as good.
Another suggestion I saw was to only lap in 1 direction (so push away, then lift and replace, then repeat) rather than pushing and pulling. Of course it's still necessary to rotate 90 degrees at regular intervals.
I personally bought the glass paper separately (I would imagine this would be cheaper than a 'lapping kit'). The grades I found were 320, 500, 800 and 1200 (probably won't go further than 800 though). Recommended is 400, 600, 800, then if desired 1000, 1500 and 2000. Glass paper has a black surface (don't get sandpaper - that's for wood
😛 ). The grades should be printed on the back of each sheet. The only other thing you need is washing up liquid (and time - and a drink).
I haven't got round to actually lapping yet, as I am waiting for some additional components before stripping down the pc. However, I intend to lap both the heatsink and the IHS (cpu) after checking first for flatness (drop of water on a glass surface, place the object on the water and check the other side of the glass).
Let me know how you get on as I'm interested in your results. I'll post mine also once I'm done.