Have you got a drain plug on your tank? if so drian it.
And wheres your fuel pump? disconect one of the line and put it in a bucket or something and it will all squirt out.
If it is well rusted save your self the future dramas get a second hand one or better yet get a drop tank.
you could get one fitted for about $700 if its a fck around $900
or keep changing your fuel filter till all the shit is gone but if it is well rusty it wont - hence the differnt tank.