Like with Neko, I did practice working with her voicebank before starting a cover with her... but BOY. For Neko I really only needed to copy the examples and write a teeny bit of a UST, but with AIKO... geez, it was nowhere near as simple. :/ Her CVVC is sooooo much harder to understand than Neko's Nekolist. For her, I did a practice with Karma which went HORRIBLY. The thing went so out of beat I was shocked... And she was SOOOO choppy I was like "?!?!?!" I stopped with that one to work with a UST that was a little more in her range (not by much, but :/), which was Can't Stand You. And... there was definitely improvement, but I did SO MUCH of the UST. Not that I mind doing it, but I didn't want to stop working untill I felt somewhat confident in my skill with the bank - enough to be able to start the actual cover, and I didn't stop for a long while. It did not take me nearly as long to learn how to use Nekolist versus CVVC LitePlus (which is what I believe Aiko's voicebank is called? Aikolist shows up on her tutorial as well.) I'm not showing those examples because they SUCK and are super embarrassing. This one is from the actual cover and is the best I was able to wrangle out of her. (Fight me Aiko). But yeah, honestly, I can't wait for her VCCV mutipitch to come out; it'll probably be a much easier time than this. (Haven't used VCCV yet but supposedly it has a cleaner way of writing out words and stuff.) Don't use this if you are REALLY new to UTAU; you'll tear your hair out. I almost did TBH.
Edit: I forgot to mention that using her became WAY easier of a time when I changed the resampler. I used Moresampler because fresamp apparently makes high notes sound tight and chipmunk-like. This song has a HECK of a lot of high notes and Aiko's a low voice, so I definitely didn't want that. Cyber Diva kinda sings in that style, but... I don't know.