I use a scalpel and gently draw the tip of the blade over the ribbed area several times. Yes you will lose some of the raised area but not enough to be noticeable...just be gentle. If you do it right the blade tip will make a ratcheting sound as it goes from dip to peak to dip on the ribbing.
Look at the coil on this Plasma gun I did...no mold line and virtually no detail loss.