Toileing: Developing a new design from a basic pattern

I use a t-shirt that I like to create a basic t-shirt pattern by tracing around the garment onto pattern paper. Then I cut out a new t-shirt using this pattern and sew it up to create a mock-up of the original garment. Once that is completed I put the t-shirt on a mannequin and draw on new design lines using my dds sketch as a reference. For this particular design, I also drape a cowl collar over the t-shirt to get the look I am after. When I am happy with the design, I mark centre back, centre front and the side seams on all the pieces, and cut along the design lines to create new pattern pieces. I then need to trace these out onto pattern paper and add seam allowance along the design lines. The final step is to create a toile of this pattern and check the fit and design on a person to see if any further changes need to be made (and further changes always need to be made!)