I purchased the springs over ten year ago, but if I recall, they were coated with cosmoline. I may have used mineral spirits and a paint brush and a rag to clean the springs, followed by washed them several times with dish soap and water, then rinse them with hot water. I always use my air compressor to blow water out of the crevices, holes, etc. I have hot and cold water in my garage which has been very handy. When I clean a part, I start with a mild cleaner (Simple Green or Fantastic) then work up to a more aggressive cleaner if necessary (mineral spirits or lacquer thinner), but it also depends if the part contains a rubber or plastic component.
Good luck with your project!