The mold putty has its uses, but very limited.
I've used it for small simple bits like duffle bags, marker lights etc but wouldn't use it for anything complex. It doesn't really work well for two part molds, and it can leave a little lip around the edge on a one part mold if you do not get it mashed down over the part really well.
On the plus side it is really easy to set up and use when you want to make a quicky mold. I've only used it for simple parts of things I don't need a ton of duplicates of so the molds have lasted me for many years.
The one place it really shines is when you want to make a mold of something that is attached to another part. It works well for things like door handles, emblems on the hood or side trim etc. Understand that it is kind of tricky to make those kinds of molds well, and you will usually end up having to sand down some resin from the back of each casting, but there is no real way to use the usual liquid silicone mold material.
Edited by Aaronw, 12 November 2012 - 01:42 PM.