My preference for a finish to wooden scales is a finishing oil with hardener. Applied about 3 times before you assemble the scales - you can then do some final sanding so that the wedge fits flush, re-apply around the wedge area and do some buffing for a satin finish rather than the high gloss from CA.

It's much easier than all the steps required with CA and is a tip I picked up from a brush maker - I reasoned that if it's good enough for brushes that have a lot more direct exposure to water, then it should be good for scales. I've had no problems so far and just need to re-buff every once in a while.

The brand I use (in the UK) is Liberon finishing oil - it's similar to tung oil so should be widely available.