When I made my son's vest, I used a regular sewing pattern but made it larger than his normal size to accommodate the pellets being added. It was a very simple pattern with a rounded neckline and armholes that were square in design to fit under the arm. This allowed him to wear the vest over any type of clothing and was easier for him to move in. The vest was large and designed to hang away from the body. The idea is the weight of the vest hanging from the shoulders, not to have the vest fitted to the body. As for how much weight/pellets to add, I just had to guess. As I sewed each channel in the vest and filled them with the pellets, I checked to make sure the vest was comfortable to wear and hung correctly from the shoulders. The weight of the vest needs to be evenly distributed to hang straight across the shoulders. It took just a small amount of pellets in each channel to make the vest hang correctly and the channels were sewn horizontally (double stitched) about 1/2 inch in width across the entire vest. I only filled about every third channel with the pellets, but making the channels is necessary to keep the fabric stable and to prevent the fabric from shifting from the weight of the pellets. I clean finished the outer edge with my serger and then added biased binding to finish the edge. I only had to wash the inner lining with the pellets a few times. I hand washed it and laid it flat to dry. I suppose you could place a weighted vest in a pillow case and then machine wash and dry it. My son wore his vest daily and sometimes he even slept in it. Hope this information helps.