These images (the 1st 2 are film stills) show the first 3 glazes as they went on, alongside the initial underpainting. This portrait was a challenge in the sense that I underestimated how light the reference was and how light the final painting would be, so the grisaille was too dark to begin with and the glazes darkened it further. It is still a challenge to find this balance in the grisaille and resist the temptation to paint it too darkly.
When the values are a bit dark in the grisaille it can take a while to lighten them, although this can be a blessing because repeated glazing has an unrivalled quality compared to only a few glazes.
Philip Guston described himself as a moral painter, and said the effort a painter puts into their art is still there in the final painting. Sometimes where the path of least resistance has been taken, paintings can have a shallow quality sometimes. But all the effort and struggle, corrections, reworking, repeated revising etc. carry a moral charge that one can intuitively feel and perceive in the final painting.
The video I made of the first glaze going on the underpainting is here on my videos page.