I have spread salt and sand with a FEL. It requires skill and lots of practice. It also depends on how "flowable" the material is.
I isn't easy, BUT you can do it. Think of getting the dump angle of the bucket to just the point where materiel starts to flow as you creep forward (HST transmission much preferred) as the material starts to flow, you must curl up slightly or you will get a "wad" of material on the roadway. Then continue shaking the joystick like a man with severe palsy. You will continue as you start to lower the dump angle again to keep the flow rate even as you match the creep rate forward. I told you this wasn't easy didn't I?

Anyway this is an advanced bucket manipulation technique, and it might take some practice to get it down. Keep adjusting/shaking/creeping until you get the desired results. It would be much easier to show you than tell you.