Checkout my post about this. I managed to dial my bed to .056mm of deviation on my first K2. Just finished making a tutorial using the second unit as an example (got it to .0780), with a bed that looked like it came from a Pringles convention.
For dialing in your leveling screws, checkout this video exclusive to K2 Plus. Before shimming, get it as level as possible using the method @Dangerous noted. The creator included some macros along with the video tutorial.
