I was curious about using the previous approach with my usual subject matter...
I managed to get a relatively good control with the free flowing ink on raw canvas. I was prudent with the use of colors, not to obliterate the ink underpainting. Knowing that a varnish will darken existing tones, I could go lighter on the ink. Also, a bolder use of colors, the next time around would go in line with the looser style I want to develop...