Used Prist for years, as a previous poster has said it is not as dangerous as some would have us believe, there seems to be a self perpetuating myth emanating from the fuelers which is not backed up by fact and which suits their self obsessed Health and safety cultures that they have surrounded themselves in.
Yes its certainly not the sort of stuff you want splashing around and a degree of common sense should be used when handling it but you should not be frightened of using it.
For prist to work correctly it has to be dissolved or held in suspension in the fuel, aerosols work best sprayed directly into fuel flow. If you spray aerosols directly into standing fuel it just sinks to the bottom as does pouring prist. Pouring prist is designed to fill tanks that supply an agitation system that mixes fuel and prist in measured quantities,these systems can be found on fuel bowsers. Pouring prist should not be poured directly into aircraft fuel tanks it wont mix, sinks to the bottom and forms a jelly like mess in the tank.
Basically prist works by attracting water particles held in suspension in the fuel, it forms larger clumps which sink into the water catch sump, once there it can be safely drained off. It is not an anti freeze it is basically a water collector.