So I went ahead and lapped my FX-8350.
I used the plastic holder the chip came packaged in and put electrical tape all along the sides of the chip while it was in it to cover the silicon that sticks out under the IHS.
I used 200 grit normal sandpaper, 400 grit wet/dry sandpaper, as well as 600 and 1500 grit to give it the final finish. At first, I was using only 400 grit as recommended but I found it took way too long to remove the aluminum oxide coating (or whatever it is). So, I switched to 200 grit normal woodworkers sandpaper I had lying around the house. I used alcohol on a folded up paper towel to wipe down the heat spreader and remove the residue as I worked. I got the wet/dry sandpaper at Ace Hardware for about $1.30 a sheet, and I bought 3 sheets total, so doing this cost less than $5. The highest grit I could find there was 1500, so it doesn't quite have a mirror finish, though it is pretty shiny and reflective. I'm not sure where you'd get 2000+ grit.
The results? I even sanded down my H100i water block because it was scratched and looked like crap after many reseatings, but I didn't take pictures of this. Anyway, it doesn't seem to have been worth the effort because it made NO difference in temps. I didn't change any of my systems settings, still 4.7ghz at 1.475v under load, using "high" LLC setting, and my cores max at 55C in Prime95, with the socket around 68C. These are the exact temps I was getting before. So, I'm not sure if it's worth the effort, even using 200 grit paper it took me two hours to finish sanding the coating off the processor, and it didn't lower temps.
This was my first time doing this and I was nervous that I would fry my chip. However, it would seem these things can take quite a beating and keep working as long as the pins don't get messed up and you don't get the thing soaking wet. I was aggressively scrubbing the thing with 200 grit sandpaper and it still works flawlessly. As long as you tape off around the edges so none of the metal particles fall underneath and get on the pins, and use compressed air to blow the particles off the tape as you work, you should be okay. For less than $5 it's certainly a cheap and affordable mod anyone can do. I would suggest anyone who is considering lapping to just go ahead and do it, and maybe you'll see better results than me.Edited by neurotix - 9/30/13 at 12:29pm