I know this thread is old, but in case someone else needs to know this, here's my experience:
I'm in the progress of making a night elf costume, and inbetween expanding foam drying and leather driving me crazy, I thought I'd crack this one.
I had some wig hair left-over from another project, so I used the wig hair, cut it in the right length, then took some very thing metal wire, rolled around the hair and painted it all white (since my nelf has white hair). I then used first eyebrow wax (or whatever it's called from Grimas theatre make-up) to hide my own eyebrows, painted my skin white-ish (my nelf's skin is that colour) and then used mastix to glue the eyebrows on top of my own ones. They do tend to get a bit "sad", but with the wire, it's quick to fix them up. Also, I had these materials lying around, so it was a cheap and quick fix for me. I think I will go with that solution when I'm done, since the mastix is pretty good at keeping it in place, and it's not that uncomfortable.