I like the dust of sneezing and choking idea, That stuff is just broken. Only downside is it gets whoever activates it also. I would say give it to someone fast, Do your best to make sure he/she wins Initiative and hope they are both within 20 feet of each other. Another option is have each PC carry a charge of the dust, and have whoever goes first try to disable each one. As long as at least couple PCs are up and running once the DMPCs are down you should be ok.