Your real problem appears to be scale:

![enter image description here][1]

I think caused by clipping plane being way beyond what is necessary.

![enter image description here][2] 

You had it set to 1mm - 1km

###Overlapping faces

My first impression is that you are trying to fix the wrong problem. I suspect that the reason you are using BSurfaces is because you don't know why you are getting scratches. The scratches is a much more interesting problem, and knowing how to fix those will help you in future modelling. 

If I am correct, the 'scratches' as you call them, are the result of overlapping geometry, and this results in `z-fighting`. The scale you are modelling at compared to the _viewing_ world scale will result big enough rounding errors to make this noticeable.


  [1]: https://i.sstatic.net/FORWV.png
  [2]: https://i.sstatic.net/O3A4Y.png