I've had 6 grays under my care, 5 Congos and 1 Timneh and although they all had their quirks, there are a few things that are common. The most noticeable ones are that they bond very deeply with people -to the point that it's very hard to make them bond to another bird (none of mine did and two were brother and sister from the same clutch that had lived their entire lives together). Because they bond so deeply with their human, they don't like to share and they need LOTS and LOTS of attention. Mine are only really cuddly during breeding season (they nest and lay eggs -Sophie CAG is still sitting on them but she comes out every morning to spend some time with me and has no problem with me sticking my hand in her nest -a cardboard box on the floor in the corner of the birdroom- and even taking her eggs) but they are always affectionate in their own way touching me with their beak and making kissy noises. Their favorite thing is to ride my shoulder -they are not touchy-feely birds but they do enjoy (on occasion and only when they give their permission for it) a head scratch. They are naturally high-strung birds and very emotionally sensitive so this added to their need for lots and lots of attention is what makes them so prone to FDBs (people with normal lives -family, full time job, etc- cannot usually provide what they need and that's why most of them end up plucking). They are picky eaters and very stubborn about trying new foods. If you persist they do end up eating a large variety but it takes years to get to that point. People report their grays been afraid of change to the point that a new toy can send them into a panic but I have never seen this with any of mine. They are not usually good bathers - Wolf's Kookooloo likes getting misted but none of mine ever did. They do bathe on their own in a large bowl of water but, although it's a HUGE project with lots of gyrations, getting in and out a million times, dipping, flapping, etc., they always end up with just a wet head

They never look or smell dirty though so I don't usually insist much on bathing them with a spray bottle.
I can't think of anything else right now but, if I do, I will come back.