I have 30+ year old Barbour jackets
wash them off outside with cold water from a garden hose
brush off mud and dirt
then, on a sunny afternoon reproof them with Barbour wax or Nikwax, once a year
go over the garment with a hair dryer to smooth out the finish
the Barbour web site has instructions
or you can send the jacket to Barbour in Milford NH and they will do it