Remove paint from the head tube I'm planning to build a new bike from scratch.

Part of that is buying a new frame, and possibly facing/reaming it. That's actually the part I'm scared of the most.

Fortunately, the brand I'm targeting, Surly, seems to do that in the factory. But as they state, there may be some paint left where it should not be:


  Since Surly frames are faced prior to painting, it is possible to
  shave the paint off the head tube and BB shell ends with a carpet
  knife blade.  This usually results in an acceptable result, saving you
  money, but we still recommend having it done the proper way to ensure
  longest life from your components.


So what is the "proper way" to remove the extra paint, if the frame is properly reamed/faced already?

Should I choose not to do it the proper way, which components are going to suffer? I suppose at least the headset and bottom bracket, but could the frame suffer as well?
The proper way to do this is to use a facing tool. Park Tool makes the BTS-1 for BB's and has directions to use it here. Theres also the Park Tool HTR-1 for head tubes with directions here. 

[You may need different tools, but the idea is generally the same. Note that some manufacturers of headsets or what not may void your warranty if you don't do this properly.]