There are several techniques you can use to apply a deck sealer. When in doubt, follow the instructions written on the container.

Applying the sealer with a brush gives you the greatest control for the most even application and will ensure that you get the sealer not only on the deck boards but in-between the boards as well. The downside? It takes a long time.

Rolling on the sealant with a paint roller is faster, but you have much less control. You might have to go over it a couple of times to get everything coated.

You can even use a garden sprayer to apply the sealant. No fuss, no muss. It's the quickest and cleanest way to get sealer down on the main surface deck, but it offers the least control for application in those hard to reach areas. Remember to cover nearby foliage to protect them getting sprayed with sealant.

Whatever technique you decide to use, sealing your deck is absolutely essential.