I like to make my models of many materials, whatever mimics the properties of what I am looking to make my final piece from. For the organic pieces I use floral foam (because it is inexpensive) although there are more dense foams used in the ID field the=at are really fantastic. And then work paperclay over the foam to seal and refine the form.
https://www.michaels.com/creative-paperclay-modeling-material/10229451.html
https://www.michaels.com/floral-supplies/floral-foam/915464296
Aluminum flashing for flat bendy things… or even in my miniatures the same material as the full scale works.
tools can be files, sandpaper, hot glue gun, knife.
I use a NextEngine 3D scanner. Although you can send your models out to be scanned by a third party.
Programs: Rhinoceros 3D, and Autodesk Slicer