I highly recommend
http://www.jgreer.com/index.htm Way over smooth-on, TAP, or Poly-tech... His stuff is cheaper, excellent quality ( I've been using him exscusively for the past 3 years), & he usualy ships the next day. His prices WITH shipping usualy costs less than other places retail price alone...
His casting resin is basicly oderless, cure to an off-white, very stable, good set time, & durable. His silicone's catylist is purple & smells like grape bubblegum... LOL I use those as well as the silicone 2-part putty, oils, & other products... Try him, you won't be dissappointed. He also sells fiberglass cloth, resins, 2-part pour foam... Everything you need for armor/prop making.
Wolf