I drew this portrait as a wedding present for my brother-in-law and wife, who kindly flew and hotelled us to their wedding in Montevideo.
This portrait took me quite a few hours. I lost count, but possibly an aggregate of 24?
For these portraits I started using a multi-pencil technique. Start with harder pencils (4H, 2H) to outline the drawing and in general get the proportions and shape right. Then gradually move into softer pencils (HB, 2B, 4B, and occasionally 8B for the blackest blacks) to increase the blackness and contrast, and add detail.
I had the guidance of my teacher Jorge Calderón wihout whose advice this wouldn't have turned out half as good.
Here you can see the whole process. out of that challenge.