I do not know the properties of VX but as we read only a minute amount was needed to kill a human and the perpetrators don't seem to have after affects of applying the agent, reads like only glove used and no other special attire needed to protect themselves. 

it also seem that VX has to be inhaled or the likes, why they having to spread on the face and not on clothes, hands, etc.  VX doesn't seem to be to hard to conceal at all.