Reversible candles, candles that are half black and half another color, are used for spells to reverse negativity that has been sent to you from another person.
A double action candle is essentially two spell candles in one - a black candle to reverse and remove negativity and a colored part to bring what you desire: red for love, green for money and white for all-purpose blessings.
To work with a black over red double action candle, you do not need to "butt" the candle - it is ready to burn as it is. 
Inscribe the black half of the candle with your enemies' names in reverse writing and dress it in a downward motion in Reversing oil. Inscribe with your own name on the red half and dress in an upward motion with an oil to bring in the improved love condition, such as Attraction, Adam and Eve, Come to Me, Love Me, Lavender Love Drops, Stay With Me, Return to Me, or Reconciliation.
You may dress the candle with additional herbs and affix to a mirror before lighting it. As with all candle spells, you will want to burn it when you are nearby and awake. When you leave your home or go to sleep, snuff the candle (don't blow it out) and relight when you return.