I agree with fenn, I don't think this would EVER be necessary unless you are one of those SUPER finicky, epically OCD people that have to have EVERY last ounce of perfection in place. THe microscopic imperfections in a heatsink will be filled by pressing the heatsink to the die... I don't see the point here, i would wager a guess that EagleEye might be onto something.
No I don't "tint", and i have never tinted any of the 1000 some odd heatsinks i have installed in my life, and there have never been an issue.