Yup, through the olfactory nerve, which is a pathway through the nose to the brain for nano particles. I am surprised they still haven't erased it from the wiki page:

Pathway to the brain

Some nanoparticles entering the nose are transported to the brain via olfactory nerve. This can be useful for nasal administration of medications.[8] It can be harmful when the particles are soot[9] or magnetite[10] in air pollution.[11] - https://en.wikipedia.org/wiki/Olfactory_nerve#Pathway_to_the_brain

Yes, chemtrails use the same idea.

It's interesting that you mention the covid swabs. A PCR test would require DNA sample, which could easily be gathered from saliva. However, they wanted people to push it waaaay, waaaay up their noses, because that's where the olfactory nerve is.

The nano particles used are graphene in it's variations. Graphene is one-atom thick, therefore, undetectable for any non-advanced bio lab. During the covid vaccines scam, medical professionals were able to detect it only because they used an optical spectrograph.