Years ago when I lived in a house whose gardens had the type of soil that baby's breath loved, I dried a lot of flowers to sell in my mom's antique shop. I had a couple of very large, shallow boxes, the ends of which I supported with two saw horses in our garage, which was very hot and dry.
Using a sharp awl, I poked holes in the bottom of the boxes and threaded the stems of flat blossoms like black-eyed Susans, daisies, and Queen Anne's lace through the holes. Then, I used a mix of Borax and white corn meal to dry the flower heads while the stems, hanging straight down, dried also. By tipping the boxes when the flowers had dried, the drying powder shifted, leaving the flowers, which I then cleaned with small artist brushes.
Although I have beautiful perennial gardens in our old Cape, I have never been able to grow the amount of baby's breath here that I did in our former home with its sandy soil.