Same here with Kennedy. TMS and Startoons are very easy for me to recognize on TTA without having to fast-forward to the credits. With Wang and Akom it can be difficult at times, but I'm starting to get the hang of it (Akom has a distinctive-looking Babs Bunny, for example). Freelance Animators is also easy to tell from the other studios, because of their weird-looking Buster, Babs, Yakko, Wakko and Dot designs. And Kennedy Cartoons is pretty much distinctive for me as well, mostly when Glen Kennedy or Jonny Mack is animating.
For telling the Warners' styles, TMS and Wang are easily recognizable to me. TMS's scene-wipe transitions are also pretty distinctive from other studios, judging by their rough-looking fast movement as they do so, and a thick black line often separates the scenes. This not only shows up on the Warners' shows they did, but I recall seeing it on some of the Disney shows they animated like "Chip and Dale Rescue Rangers" and "The New Adventures of Winnie-the-Pooh."
Oh and Speedy Boris, I see you've made your final decision that it was really Kennedy Cartoons that animated "New Character Day" and not Wang. I agree with you actually. Throughout watching the whole episode I could tell it was Kennedy's work, and during the creits I was expecting them to list Kennedy, but then when the Wang credit came up I was like, "Oh, I forgot this was the Kennedy episode that was miscredited to Wang!" I think Wang COULD'VE done the ink-and-paint work for Kennedy like they did on "High Toon." But anyways, I even submitted the info to the BCDB entry on "New Character Day" about the miscredit.