I know that people use two methods; they either atach the plants to the bogwood using weaving/fishing string, or using a hairnet. I nor shure of all of the plants that will get to the bogwood, except for java and christmas moss. Of course, i had some valis that grew on one of my bogwood by itself, it anchored to the wood by the roots, it looked pretty cool!
Agreed on the cotton front. Whilst fishing line, hairnets etc will always be in the tank, if you use brown cotton, it's difficult to see to begin with, and then by the time the plant has become well-rooted to the wood, the cotton rots off. Perfect!
I have always found cotton thread disolves before the plants become well attached. I hate nylon fishing line as it is a pita to knot . I use two different methods now: waxed dental floss - it wont disolve but needs to be removed after the plant roots well, and black nylon wire ties. These come in different sizes and can be ganged together if needed.
It is also possible to use staples to attach plants to wood. yes they will rust, but iron is not harmful to a tank and they are so small it really is not a caoncern.
One note- if you keep plecos the thread or dental floss can snag the plecos as they graze the wood surface.