I had the same suspicion at first regarding the nail polish, but he does it whether or not my nails are painted (the color doesn't seem to matter either), whether he's on my shoulder and my hands are hidden from view, whether he's on my finger.... it's the same wherever he is and whatever he's looking at, as long as he's with me. EXCEPT..... I discovered the other night that he seems to really like being swaddled up in a scarf and quiets down/starts grinding his beak during scarf cuddle time.
And then, of course, he gets tired of scarf cuddles, runs up to my shoulder, and goes back to peeping.
I wasn't able to try handfeeding him last night either as his crop was MUCH too full!
Do you have any recommendations for a safe fleece thing I could keep in the cage? I'm wary about having fabric items in there as he's already gotten caught in a thread once (under supervision, luckily) and I'm terrified of having that happen when there's no one around to free him.