I have been using cotton filters in my glass mouthpiece tubes for about a week now with very good success. You can see from the photo how much it filters out. Very similar to a cigarette filter. The best part about it is that you can take the dirty cotton filter and place it in the roasting tube so that the oil can be re-volatilized again. I have gotten hits bigger than I have had by dabbing from roasting the dirty cotton. It gets so concentrated on the cotton and seems to work better than just cleaning the tubes with cotton / alcohol. The cotton fibers don't get all matted down so the air flows through it better.
I place just enough cotton so that it will stay in place, but not enough to hinder the air flow all that much. I'm not sure what size oil droplets get through, but the larger ones get trapped in the cotton. If only the smaller droplets get through, then they should have a better chance of getting deeper into your lungs. There must be a way to measure the size of the droplets. Maybe with a laser.
They do make a very fine fiber from hemp that would probably work just as well as cotton.
The cotton filter should work on many different vaporizers. Don't position the cotton too close to the heat source or you will just volatilize the oil rather than filtering it. When the air flow gets poor, it is time to change the cotton filter. I always look forward to that.
Wax / oil wrapped in cotton works very well too.