At the very moment, no, you can’t draw on several layers at the same time, but we are really considering the feature, as it could serve other purposes than material edition.
However, you will see during the livestream (around 56’ and 1:02’), it is possible however to use a texture several times in materials (of course, it’s yours then to make the proper calculations to display the needed result).
To watch the livestream : https://www.youtube.com/watch?v=GDgUe7UGqNo