Bluenote, I suggest you don't add scents to the brine cures. That way it allows for trying different ones added out on the river until you match the bite mood that day. Put bait oils right on the eggs and some on the yarn and they will stay on effectively. You can reapply more about every third cast or so to freshen up the bait. I think that's better than adding it during the curing process, with either brine or powdered commercial cures such as Pro Glow or Pro Cure.

As for over staying them in the brine too long to make the eggs too hard I suggest cutting down the time in the brine like Bob said, so they retain more softness and milking ability. Then the day before you use them you can dry them harder for fast water use or leave them moist for slow water use. my .02