The dark clothing is taking a long time to cover. I don't want to rush this stage as there has been so much work put into the face that it would be a shame to spoil it with a poor background. Also, the habit is an important part of the nun's character. It says a lot about who she is and it substitutes for hair in providing a frame for the face. I have decided, however, to keep the folds simple. There is little movement in the posture of the figure and I don't want to make any folds look contrived by inventing what isn't really there.
The first layers were built up very gradually with light and swirly strokes. See the video below.
Then, I used a Derwent blending pencil to deepen the tones. At this stage, I am halfway through the blending process. The photo below shows the portrait before blending. You can see that the colours are very much more subtle. The blending gives a more painterly feel to the fabric.