How should I protect my deck?

uming its wood, you could use a low volume Pressure washer,but this would probably 'feather' the wood.Try using a wire brush lightly,this should work.If concrete use pressure washer. After brushing with the grain,you could use a pump up garden sprayer with a high quality Silicone,to reseal the deck,use generously.Wood wears with traffic so anything is going to have to be reapplied, at least every 2-3 years to maintain wear and protect the wood.If its concrete they have a rubberized roof coating that stands up pretty good.