Most new waterproof items, while they still have their factory DWR intact, don’t need an aftermarket product since their original coating is highly effective. There are a few exceptions, such as using a dual-purpose tent spray, like Nikwax Tent & Gear Solarproof, that’ll protect against solar damage.   “The other thing would be items that aren’t waterproof and breathable, like a rubber rain jacket or bibs, like commercial fishermen wear, or like neoprene, rubber rain boots—you don’t need to use it on those types of things,” Allen says.