my favorite resources i've found for HANASU stuff are these videos by Haruqa (the person behind a lot of TTS stuff, like TALQu). They're all in Japanese but they should be at least a good visual and audio guide on a couple methods. They also include all links to plugins they mention in the descriptions
this one goes over a few plugins that will allow an UTAU to speak. these are a much simpler way to get into making UTAUs speak, but don't always sound the best on their own. i like using these as a base sometimes.
this one might be more what you're talking about. by using the multi pitch editing tool, it's easier to simply draw natural sounding tones for speech.
Hope that helps somewhat ^^