This Great Dane (called Oakley - from a photo by Robert Reid) is the first dog I have painted entirely with a palette knife. It is a small painting (8"x6") and I had a few moments of thinking there was very little point using a knife instead of a brush when working at this level of detail, at this scale. The whole point for me of using a knife was to force myself to work more loosely.
My downfall was his eyes. I can't bring myself to paint eyes loosely, they are very important to me.
So I ended up using the side and point of the knife - an awkward and inflexible 'brush'. Doh.
I will have to see if a brush/knife combo will work or not for future portraits. Either that or I must overcome my desire for well-rendered eyes. I checked out how my hero David Hockney managed to resolve this: that master of loose brushwork.
One of his books is entirely devoted to paintings of his daxies. Guess how he does it? He paints them more-or-less exclusively when they are asleep. Yep. That would work.