Ashrod – You still out there??? I don’t come to this forum often and just saw this post. Short version: I’ve made many 2-piece jig molds from Durham Water Puddy (DWP). Yes, they do have a fairly short life span. Now I'm up to maybe 30-60 jigs depending almost entirely on quality of mold. I'm slowly getting better. I suggest to first totally master all aspects of making 2-piece DWP molds for pouring soft plastics, like, make at least a dozen useable 2-piece molds for plastics. Soft plastic is waaay more forgiving then hard bodied jigs. After mastering soft plastic molds then try making one for jigheads. Vitally important that the jig master (mandrill) NOT be submerged in DWP past it’s centerline. Gotta be right on, not a nano too deep or too shallow, or you will not be about to remove the master from the hardened DWP. This is waaay harder to do than you might think.
Finally, and most important, the 2-piece mold has be absolutely bone dry before attempting to pour molten lead. I’m sure you are well aware than molten lead and wet stuff don't mix without getting ugly.
Following is another thread I wrote a while back that might hold more information.
Just let me know if you need more info on this.
http://www.tackleunderground.com/community/topic/21344-making-dwp-molds-for-jigheads/page__fromsearch__1