How to clean my backpack?

I have a furry backpack.LOL.
I've already washed it and its clean, but the stupid bottom of it is still dirty
Like it has gray thing's that just wont come out. I've tried brushing it, and using 409 while scrubbing it but its still in there.
The bottom of the backpack has shorter fur than the rest of backpack so thats why its so difficult. HELP !
and i dont wanna trim it cuz that would look really dumb :p
~thnx~
i tried to brush it -__- it juss wont come out n i cant go to a dry cleaners right now.im busy n hav to use it 2mrw