@Pearl, I used polyester wadding. 2oz to cover the mannequin, then 8oz for padding, this of course depends on how much padding out you have to do
You can then tease it out to get the shape. My dummy was bought a size smaller than me ie 12/14 for 16/18 I also bought some L shaped rulers, they were carpenters ones off eBay for £15 for 2. You need to know the depth ie front to back as well as width of the body
I then made a tight fitting calico hip length bodice with princess seams. It had no ease whatsoever and a friend pinned in on me to follow my
contours bulges. So open ended zip allows you to get it on and off you and the dummy.