Here I am again , I have finished blowing my varnish onto the painting. I blow just enough on there to bring it up from being dried in. Next I blow through the longer leg to clear any varnish which may have remained inside. I don't need to actually put my mouth onto the tube to do this , I blow from an inch or so away.
If I need to, I can clear any obstructions with an E string from my guitar, the wound one, not the thin one on the bottom. Florists wire works , particularly if you send it through there after a little turps. Or you can soak a pipe cleaner in turps, that works too.
I suppose I should stress you want to step back each time you take a breath to blow more varnish. Just like from a spray can you get a certain amount lingering in the air before it settles. All of this is really simple compared to drawing feet.