Get a large pillow with a zipper that measures LARGER than the body you want to duplicate. Put the zipper at the bottom (the hips). Stuff it SOLID with any kind of fabric, towels are good. Use duct tape or packing tape to cinch it to the right size bust (measured under the arms and under the bust) and waist (smallest part) and hips. Add a bra and stuff it until it’s the correct measurement (across the fullest part of the bust). Tape it to make it smaller if you have to. Measure from the shoulder down to the fullest part of bust (on yourself) and adjust the straps of the bra to put the bustline in the right place. Cover with a stretchy t-shirt to make it smooth. Now you have a stand-in body double model to try garments on as you knit/crochet, so you can make a perfect garment every time.