I did a 1 inch to the foot set of drawings for the coming HO train layout. Took my time, did several trial drawings, copied the best one over on a clean piece of paper. Used squared paper, compass, architect's scale and the resulting A size drawing was nice and neat.
Next step, draw the track work out full scale in the actual layout table. Bought a dozen sheets of white poster board and covered the layout with them. Tacked the poster board down to the foam with drafting tacks and started drawing the track plan out full size. Used a trammel (long piece of board with holes for pencils) to swing the 22 inch, 20 inch and 18 inch curves. The centers of most of the curves are off the bench work out in mid air. I used a yard sale photographic tripod to give me a center to swing the trammel on for the airborne centers.
Partway into all this layout work, I began to change the plan. All sorts of things that looked great on the scale drawing, began to look less than great at full scale. So, out with the powered eraser, and change things around. Lesson learned, always mockup things up full sized.