I recently made a sale on a painting that I made last year. When I got into my storage, the painting has a lot of dust all over it... I don't want to varnish and send the painting till its cleaned... but I have no idea how to actually clean it. I found a kit on Amazon for $50.00, anyone have any suggestions they tried themselves. I believe the one I see on amazon says its to clean a painting that has already been varnished... what do you do to clean a painting that has not been varnished. Thank You.