Slap your with a hairbrush for 5 minutes straight, hitting at least 100 times per minute. That means 2 smacks per second. Don't give yourself any breaks. Use medium to hard force. If you stop, you have to start over. Lock yourself in your room until you've done it right.
Trust me, you'll be wailing up a storm and regretting whatever you did to warrant such punishment.
Also do what Tee suggested, use a bathbrush or scrubbing brush to exfoliate your bottom till its red. After reddening your butt, rub some mineral oil over the freshly exposed red skin. Then, wallop away.
This resource may be of use:
http://selfspanking.org