I tested the erasable carbon paper from  CopyRite.

Transfer of a drawing onto watercolour paper.

Very good results : Does not stain the paper. Lines can be erased without leaving any marks. Perfect for transferring properly  without being afraid of getting the paper dirty. It can also be used to transfer a design onto canvas or  fabric.  Several colours of carbon are available : black, blue, red, yellow  and white which is convenient for transferring on a medium of any colour.