I'd discourage anyone who takes drugs up their nose from "aggressive" blowing actions, whether it's with bottled water or the air in your lungs.
It isn't going to get rid of cooties, and you might just force drug or cut agent, dust bunnies or hairs, deeper into your sinuses, or damage those septa worse than they are.
Whatever straw you use, I'd try to avoid forceful deep insertion (into your nostril; with consent, it's encouraged elsewhere) so you don't zest off more nasal tissue.
I think the cocaine users, with frequent redosing, and pleasantly numb to how their shit would burn as bad as crystal, with chunks of bloody septum falling out of their faces, are the ones who need to worry about the flora and fauna on their drug straws. They are more likely to massage raw tissue with a straw that someone else massaged their tissues with.
Fellow meth snorters, we should worry less about the bill that barely touches skin on our faces, and seriously think about the one that crushes the stuff. That goes straight up our nose to incubate.
The HR folks will leave out the astronomically long odds part in warning of HIV or HCV through shared straws (HBV is much more likely) but the one that'll get you is plain old staph. That shit's already on your body, and rather than kill you slow, it'll kill you fast. So the hygienic route is hygienic: wash your hands.
Really, it's about taking a break before your nose is an open sore, and staying healthy enough through self-care that simply breathing through a dollar bill doesn't get you sick.
(FWIW: I like to use a plain post-it note to make straws (and it seals itself!). They come in pre-made stacks too.)
