In order not to get stung by a wasp nest, you will have to wear protective clothing. You can still get stung through a bee suit. Yet, this is the best way to protect yourself from stings. Homeowners should not attempt to treat wasp nests unless they have a bee suit.
Nighttime is the best time to treat a wasp nest, since they are all back at the nest. Fast-acting insecticides will kill them before they can leave the nest to sting. If you do not have a bee suit and choose to do it yourself, then treat at nighttime.
You will also want to keep your distance. That is why wasp and hornet spray is advertised to reach the nest from a distance. The further away you are, the less likely they will sting. Bee exterminators use bee poles to provide distance between themselves and the nest.
Wear white. There is a reason bee suits are white. This is the least aggressive color in the minds of bees and wasps. This isn’t to say a white t-shirt will protect you from stings. But a white bee suit will.