packing foam ......would make great snow drifts but not sure it would work for flowers.
Thin sheets of foam seemed to work well .
Makeup sponges gave a smaller more dense crumb and the humble kitchen sponge worked well too. (although Im not sure if I can find white ones)
There are lots of tutorials for home made flower soft on the net so I thought Id give it a go . Here are the results using different foams. ( not dry yet but wanted to share it :) The first thing I did was grate the foam. I then added the gratings to water ( the amount didnt seem to matter) and used my stick mixer to blend it up more . I then strained the foam from the water and added some colourings to some just to see how they came out . :) Interesting results and different textures .