Well not that bad, I've done quite a few times already actually, not a fishing line but with a piece of string. Yes, beta link is the right way to go if you want it completely sealed and no gaps, no mess at all. I used a medical syringe with no needle to lay it on the spoiler very thin, remember once you press on it it'll spread nicely. No need to use a lot, whatever you do don't use the plastic tip that comes with the beta link unless you want to make a mess lol
Grigio Telesto M4, 6MT.