Glad you asked--it seemed a little brittle at corners and thin ares--maybe I didn't bake it long enough--I don't know. It cracked when I was drilling it. I probably wont use it again for anything that needs to somewhat durable.
JB weld type putty is way more tough, but some of them are hard to smooth out because they cut it with a sandy material. I've been looking for a type I used years ago to make a comfy grip for my BB-gun. It was great because it took 10 minutes to harden (longer than most) and it smoothed out REALLY well with a wet finger. The finished product looked really slick.
I would use Sculpey to get the shape I wanted, then re-do it with the JB--look for the 10-min kind so you have more time.
Another thing I always mention about JB that is so cool is that you can put wd-40 on a bolt, or something threaded, press it in and let it dry, the oil allows you to simply unscrew the hardware out. and you can bolt things to it. I made a threaded insert for my DSE atomizer(like the battery end)and it screws in perfectly.
Good Luck!