The rubbing gives it some interesting variations that make it look similar to a watercolor. Robert Rauschenberg used it to great effect in his illustrations of Dante
The painter Willem de Kooning used reproductions of one painting he was working on to transfer bits to another. This would create an interesting application of paint on the painting as it is rubbed on rather than applying using a brush. He also covered his paintings in the newspaper between sessions, which kept the paint from drying out. This had an inadvertent effect of transferring some of the print into the painting.
The transferred newsprint remains aligned with the canvas’s edges, enforcing the tenuously grid-like structure of the painting.”–The Metropolitan Museum of Art.
Another innovation deKooning made was whipping up oil paint, water, and Saff-O-Lite safflower cooking oil to create a frothy mixture with a slow drying time and a very liquid effect so he could work for months on the same painting. Unfortunately, cooking oil is usually modified to prevent spoilage, so it doesn’t really dry. Parts of a painting he made in the 1970s, is still dying, and there are small leaks where the paint is still flowing:
nearly eleven feet tall and weighing almost a ton, the work’s dense, the multi-layered surface became, in DeFeo’s words, “a marriage between painting and sculpture.”