I used linseed oil (rubbed on with my finger) to retouch two small portraits. I wanted the surface to stay wet a day or two so did not want damar retouch which dries too fast. However, the linseed oil, thinnest coat I could manage, stayed sticky for several days. That was ok: I waited it out. However, now the irritatingly slick surface in the retouched areas is a problem. I want to work on the paintings further. I wish I could sand the slick surface with 600 grit paper to restore some tooth. But this is too scary on a stretched canvas which doesn't lie flat. Is there some way to take away the glassy shine without sanding and without removing the paint underneath? A tiny dilute amount of turpentine? Or, apply wax medium or maroger on top of the dried linseed oil?