This spreader is one of those pieces of equipment that has a long history. It had been used on my childhood homeplace by my dad for countless years before we acquired it over 40 years ago.
The power washer is used to blast the residue from the equipment. It works best to break up the cleaning into different days. One day to breakup the larger, cement-like, build ups while giving the tractor and spreader a good wet down to soak and soften the remainder of the residue. The second day to go over all the spots again and clean off everything is usually enough.
We had a good rain shower roll in as we were finishing on the first day to assist with the task of wetting down all the surfaces.
With this job and cleanup complete, the spreader will air dry in the barn several days before applying a thin layer of oil over the entire piece of equipment to protect it from rusting until it is needed again next year.