[caffn8me]

I was at a M·A·C Pro training evening last Friday and the MA demonstrated using a 217 brush with Select Cover to get a very natural finish to the concealer. Apply very small amounts at a time to build the cover up until it's enough but not obvious.

Another option is to neutralize the undertones before applying a concealer. If the shadows have a blue undertone you should use orange (I've seen Rule eye shadow used for this before very effectively) or if the undertones are purple, use yellow. Then apply concealer on top. You'll need less concealer by doing this than you would by using only concealer. Don't overdo the correction though!