Any oil can be used for dressing a candle but initially it is best to either use your favorite essential oil or an oil infused with a suitable herb for what you are about to do. There are various ways to dress a candle but what's important is the direction in which you anoint it. Working from the top down draws power from spiritual sources, while working from the bottom up draws energy from the Earth. If you rub the candle with an up and down motion, you'll end up confusing the energies.
To dress a candle, you will, of course, need your candle and the oil of your choice.
A simple method:
Sit quietly holding the candle, think clearly about your intent. If you have learned to meditate, then enter a meditative state and allow the energies to build up within you.
To bring something to you, rub the oil in a downward motion from top to the middle and them from the bottom to the middle. To send something away from you, rub the oil from the middle of the candle out to the ends.
Continue with either movement until you have a sense you've done enough.
If you have remaining oil on your fingers you may rub it on your hands until it has been absorbed or simply wash it off. You may also dab it in your forehead to help you connect with your Third Eye chakra. Keep in mind to do research about the oil of your choosing, making sure it does not irritate or damage your skin. Now chant:
"I cleanse and consecrate this candle in the name of [chant the entity's name if you chose to work with one]. May it burn with strength in the service of the greater good."
Now you're all done and free to use your anointed candle for its given purpose.