I have been making war games scenery for a while (along with everything else) and been using Hirst Arts plaster molds to do it. I was getting fed up with using a board with sponge on the bottom and having to hit it with your hand while filling it with the other. so using mostly bits left around the house i made a Vibrating Board (V.001)
Would like to give a HUGE shout out to http://www.hirstarts.com
for supplying the worlds best molds. Been using them for a while and there is nothing but all round love for them.