If your trying to become the next Busta Rhymes, Tech 9 or Twister.There are 3 techniques to helping you rap faster. It not necessarily the spend of your lips, its more so the speed of your tongue. How strong it is or how week it is. This can help in so many different ways.If your tongue is strong you can rap a lot faster if it's week you can't rap as fast. So you half to have a strong tongue in order to rap faster.
Now to get your tongue stronger is by using the lalalalalala technique. This gives your tongue more muscle. I would practice this daily if you want to rap faster. Some of the artist that I work with use this particular technique and there spitting there words out a lot faster.
Secondly talking a lot gives good exercise to your tongue. If your working at a job that requires a lot of talking,than your in really good shape. Having a customer service or telemarketing job, will help you gain a lot of muscle on your tongue.
Lastly, choosing your words wisely. Don't choice words that have to many vials A E I O U. Its makes it harder to pronounce. You want to use words that will roll off your tongue easily.This helps everything that your saying to flow better and the person that hears you rap understand what your actually saying. Practice these 3 techniques and you will be rapping faster in no time.