A sewing dummy, which is also known as a dressmaker's dummy or a dress form, is an invaluable tool for ensuring a perfect fit for your home-sewn or tailored vintage garments. Unfortunately, professional sewing dummies can be exorbitantly expensive. Luckily there is a less pricey method for creating your own dummy that will be exactly the same shape as you, which is even better than commercial dummies that come only in standard sizes.
Put on the T-shirt. Choose a shirt that you never want to wear again -- you'll be cutting it into pieces. The shirt should reach at least to the bottom of your buttocks.
Ask your friend to begin wrapping you with the tape. She should begin around your waist, wrapping snugly but not compressing you, and keep spiralling down until she reaches the bottom of the T-shirt. If you have a bust, she should then wrap the tape diagonally down from one shoulder between your breasts, around your back, and then back up to the opposite shoulder. After this, have your assistant wrap around your bust but again, without compressing as you want to make sure the sewing dummy has your actual shape. If you would like your dummy to have sleeves, your assistant can wrap those as well.
Direct your assistant to cut slowly and carefully up the back of the T-shirt, cutting through both layers of tape and the T-shirt, but not any garments you may be wearing underneath. Have her help you slide the dummy off of you. Once it is off, tape the back together and then tape shut the neck and arm holes.
Assemble your umbrella stand which will serve as the base of your dummy. Lay your dummy on its back so that you can turn the umbrella stand on its side and prop it up so its pole is parallel to the ground.
Spray the upholstery foam into your dummy, filling it but leaving room for it to expand and fill the cavity, holding the umbrella stand in place. When it is dry, stand your dummy upright and tape off the bottom of your dummy to seal in the foam.
You may want to create a covering for your dummy out of a layer of batting and cotton to make it easier to pin into. Don't make this cover too thick or it won't be your shape any longer. If you'd like your dummy to have a neck, wear a turtleneck for taping or wrap a piece of fabric around your neck and tuck it into the neck of the T-shirt so your assistant can tape over it.
Avoid doing this project in a very warm environment, as you will be encased in plastic and unable to move for some time, which can lead to dehydration or heatstroke. Be sure your assistant knows to be very careful when cutting the dummy "skin" off of you, in order to avoid injury with the scissors.