don't get anything but food grade. period. btw shop around online cause some of them are price gauging and others give u the same quality food grade stuff for the cheap price it should always be.
and a normal cheapo mask will do when using it, even though i have a specialized mask with internal filters for use with pesticides etc.
used as a drench, sprayed on with a sprayer, just don't use to much or sprayer will clog. and u already know u can top dress with it too. can also be used to mix up you medium for organic soil/ soiless grows to kill anything that might be in there.
i know joker does it that way, i have done all the other ways myself and will start doing it jokers way too.
u can also use this shit internally to help rid your self of worms in your body. and that goes for dogs and cats too.