Yep, Lapping is the best thing you can do. The less heat paste, the better. it does not matter what type you use, compated to sollid, they all "suck".
As it is not possible to make a solid cpu and waterblock in one, we have to deal with it.
With a compleate flat surface, you won't need heatpaste at all. Just press the air out, and it won't come lose. (like 2 glass plates) Ju might want to use some silicone oil for the micro gaps.
There are construction factories who can do this. I'm not sure if they will do it for a private person, but it will be costly
And as we like DIY, a mirror, sandpaper up to 3000, polish, as3, as5, ketchup will do wonders. (as3 and AS5 used for lapping) (ketchup contains accid, and it laps the last micron's)
Please look also at :
http://guides.pimprig.com/modding/mi...sh_lapping.php
http://www.stellafane.com/atm/atm_grind/atm_rough.htm
http://www.stellafane.com/atm/atm_grind/atm_fine.htm
http://www.stellafane.com/atm/atm_polish/atm_polish.htm
After you have followed the guides, you know what I mean, and you'll have the lowest temps possible with your current gear and setup.