Using a combination of Gloss Medium with a little High Flow Medium (to make it flow more easily) in a Fine Line Applicator, lines were drawn on a dry piece of Saunders Waterford Cold Press 140lb/300gsm watercolor paper.

 

 

The next day, apply a wash of your desired watercolor(s) over the surface. 

 

Once the wash is thoroughly dry, use a slightly damp paper towel to gently rub over the raised acrylic lines, removing the dry watercolor from them, but not from the paper.