My sketch was made at a scale of 1"- 1'. I put a one foot grid on the canvas, and a one inch grid on a copy of the sketch. Then I could easily transfer the sketch to the canvas at full scale. I like to use a pole with a charcoal tip to do the intitial sketch on the canvas. This allows me enough distance from the work to see what I'm doing. After the sketch is completed and refined, I can start laying in the sky.