I also noticed that the surface is very important to get a good scan,
white or light gray and matte as possible, and one uniform color, and especially no black or dark colors.

I guess some hairspray should also dull the surface a lot, and is easily removable.

I looked into some special spray cans, that spray a matte white powder on the surface that can be brushed off.
http://www.laserdesign.com/3d-scan-spray/
https://www.igo3d.com/en/3d-coating-spray.html