Basically, the trick is to include more inline rhyming and triple rhyming. If these words are new to you, here is a simple explanation. Inline rhyming, as it sounds, is, simply, a rhyme in the middle of the line of the poem or song. When employing this method, you don't necessarily have to rhyme in the traditional sense (rhyming at the end of the word). Rather, you can mix it up, and rhyme at the beggining of words. This is alliteration if you are using consonant sounds. Also, you can try rhyming sounds in the middle of words. This is called assonance when using vowell sounds and cassonance when using consonant sounds.
Next, Triple rhyming is a rhyme which includes the last three syllables of the words involved. For instance, rhyming "glittering" with "twittering" would be a tripple rhyme. In music, tripplets are fast sounding notes; thus, it makes sense for triple rhymes to be fast sounding rhymes. Also, Triple rhyming may coincide with inline rhyming; in other words, there may be a triple rhyme that is also an inline rhyme.
Putting it all together:
Now that you know the rules, you can break the rules. What I mean by this is that you should make up your own words or add false endings to words like Snoop to achieve the desired results. I have written something small for you to see the effects of my trick.
Here it is:
(takes a few seconds for rap to begin)
Spiteded knitteded sewing my words.
Fiteded wit itit; hat on reverse.
Now, try saying that quickly, and you will see how it speeds up your rapping.