Whether a fader is easy to clean or not really depends on how easy it is to take apart. That's how a standard contact fader works and it's why gunk getting in the fader can affect the signal, plus it's also why they eventually wear out. Then there is a rail and attached to that is the piece of the fader that you move, which has some brushes on it that touch the tracks. Inside the fader is a little board with some tracks running along the length of it.
Some faders are easier to clean than others. Given that you've clearly never taken a fader out of a mixer and cleaned it before, I would buy a spare (it's handy to have one knocking about anyway), then take the original line fader out and try and clean it. You're lucky, in that replacement line faders for that mixer are only about £15. Dust and other crap gets into the fader and because of you moving the fader up and down when you're mixing, it gets pushed to one or both ends which can cause sound to bleed through. With those types of faders, it's usually caused by one of 2 things: -ġ.
