Writing voice descriptions doesn't quite follow any certain formula. They're meant to be specific enough to set utaite apart from others yet be vague enough to be the opinion if many people. Good adjectives for voices can be found, in my experience, from the comments and tags on the videos and from their nico nico dic entries (if you can read them). We usually just grab about five appropriate adjectives and squish them into a coherent sentence ^-^;;
Another component for voice descriptions is special characteristics of voice or style, if there is anything interesting to say. For example, Ayaponzu＊ is the "Tongue rolling princess" and Limone-Sensei sounds like Kamiya Hiroshi.