In the army the biggest concern was getting a good seal, and we tested it using a bag with a banana scent to it being put over hour head. If you smelled banana then you didn't have a good seal. I don't know the exact formula they used but I would guess anything that had an noticeable odor would work like bleach or vinegar.
As for filters I read a lot about keeping them fresh but that is mostly from the filter manufacturers (go figure), I think the biggest thing is to practice making sure you have a good seal.