Only three characters
require the unlocking of expert ghosts: Funky Kong (4), Baby Luigi (8), and the second Mii outfit (all of them). The other two time trial characters, Birdo and Toadette, just require you to
play the courses in time trial, not beat. Every other staff ghost in-between is just working for vehicles.
People, unlocking the expert ghosts is
not that hard. I speak as someone who actually managed to get them all, and is close to
beating some of them on a couple tracks. Throw the wheel away, get a heavyweight, and practice with sharp-drift bikes (i.e. the Flame Runner). Try them on a Grand Prix or multiplayer matches until you get the hang of them. Look around online and see where shortcuts to use your mushrooms are (in a lot of cases they'll be pretty obvious, like on Mushroom Gorge, which should be an
easy course to get an expert ghost on). Don't race the staff ghost, just try it solo, and then if you don't get the time you need, race your
own staff ghost until you can beat that, and again and again until you get it. Just take it slow, jump around to see what courses you do and what courses you can't (I'd recommend saving Shy Guy Beach for #32, frankly, and also use a
lightweight character there). When you get Funky, start using him exclusively. It's not that hard.
None of this game is, if you know how it works.
EDIT:
I think it said something about a "fast staff ghost".
That IS the expert staff ghost. That means you've unlocked it. You don't have to race it.
Also! Mario Kart Wii is kind of funny when you unlock stuff outside of Grand Prix. Whenever you hit a requirement in Time Trials, you need to exit everything and go back to the title screen, and then pick your profile again. It will then give you the character or vehicle you unlocked. If you turn the game off and turn it back on, it'll do the same thing. It's weird, but you'll get used to it.