Softwood chippings aren't as good as hardwood chips, but a lot better than mud! We've finally settled on hardwood chips. They're not cheap, but they last for ages.
You can use Aubiose (we use it in the henhouses), or Hemcore/Rapport, but they're jolly expensive for covering a run of any size. Plus, if they do get wet, they absorb the water rather than being free draining.