Here are the casts I've already done. Some are not on the shot, they are in place in Jabba's Stands (cantina tables and Watto's Box chairs).
Some of them are made in resin, some in plaster, others in air dry clay or foam clay.
Some parts are as they came out of the mold, others have already been worked, and some others are finished, ready to be incorporated into a diorama.
I used different techniques as classic silicone mold, re usable material (put block in warm water, and apply, I have forgotten it's name), and undryable clay called Plastiline.
Of course, there are fails, I will try to use them after some work on them, or throw them in garbage...
Plaster castings are very sensitive to moisture and require a protective layer/fixative. They are also very fragile, and do not like shocks at all, and some of them have come out of the mould and caused damage.
Air drying clay musn't be used in closed molds. An IG-88 fails, even after 3 days of drying.
The best is resin, but it cost much more and requires protective equipment.