Avoid use of oils and lotions because they can trap the chemicals and thereby prolong exposure.
We recommend using a water or alcohol-based sunscreen (rather than oil-based). If your choice is between oil-based or nothing, we advocate using the sunscreen. Pepper sprayed on top of sunburn is not good.
We also recommend minimizing skin exposure by covering up as much as possible. This can also protect you from the sun. Don't forget a hat.
Gas masks provide the best facial protection, if properly fitted and sealed. Alternatively, goggles (with shatter-proof lenses), respirators, even a wet bandana over the nose and mouth will help.