by davekeiller » Wed Aug 17, 2022 6:37 pm
You want to use tech wash or equivalent to clean the jacket first. Over time, oils and dirt build up and clog the "pores" in a breathable jacket, so you want to get the jacket clean so that it's breathable.
This may be enough to revive the jacket, but if not, Nikwax TX direct will renew the water repellent surface coating. Whether you need wash in or spray on depends on whether the jacket has a liner or not.