Find a rhyming dictionary, flip to different pages and look at the entries while you freestyle. You’ll find yourself adding a dozen rhyming words to a single line, and it will remind you of words you may have forgotten or never think of while you’re on the mic.
It’s easy to get stuck into always using the same few dozen words in key places when you freestyle, or get stuck always using the same rhyme even when you know there’s a better word out there. It can be like a lyrical cul-de-sac. So it’s always a good idea to study rhyming dictionaries when you’re not on the mic; some of the best freestylers study them every day. Using a dictionary live, however, will definitely have you using some words you’ve never thought of using before.