for me speed painting started in the studio, I had a model for 2 hours, all I could afford, I spent 20 minutes limbering up and testing light shaddow pose composition etc. I would do a complete sketch in sanguine or charcoal in 5 minutes.
then I would break for 5 minutes and consider what had taken place, usually I would be inspired to go back and start over on one of the poses, change it slightly, then draw the model for about 1-1:20 minutes at the end of that I would ahve a good sketch to take away for working up a painting later.
these days with digital concept work I will often thrash out basic ides in 15-20 minutes, but they are unrefined and rough (though still incisive and to my mind good) Ill usually have 5-10 concepts floating around by lunch time and spend the afternoon refining one or two of them.
for me there is also a benefit in allowing myself the freedom to mess things up, allowing myself to express without inhibition or fear of getting it wrong, there is no right. allowing myself to be, rather than do, means I am free to create and be created.
a belief will only find itself

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