The cotton taste shouldn't be from the coil, metallic hot legs are a totally different flavor of YUK. My best guess is your cotton is too tight in the coil and when you add juice it swells and can choke the coil thus slightly burning the wick giving you taste. Just add enough cotton to just slide back and forth with almost no friction, prime and give it a few minutes to soak up and swell and/or several good unpowered primer puffs. You can get a cotton taste but if its wicked right then the taste is minimal and short lived but cotton like rayon should have no breakin taste if wicked properly. The stronger and longer the breakin taste lingers tells you its poorly wicked and rewick it again and again till its right. I gave cotton the toss when I got my first rayon wicking and haven't used cotton since but wicking with rayon is different from cotton but once rayon wicking gets mastered, you'll never use cotton again.
If I was buying premade unwicked coils I would take the torch to them and burn it good since you have no idea who or what those coils have touched and picked up in its travels to your hand.
Your type of cotton can be the culprit also but chances of that are slim unless your using the cotton plug out of a pill jar.
Good luck on your journey.