Yes, it is generally a very good idea to seal your deck after pressure washing. Power washing removes not only dirt and debris but also a thin layer of wood, leaving the surface exposed and more susceptible to weathering. Sealing is almost always needed after this process. After a general cleaning, sealing isn't automatically necessary if the existing sealant is still intact. You can test the surface by placing a few drops of water on it. If the water beads up, the sealant is working. If it soaks into the wood, it's time to apply a new sealant. If it has been a few years, it's wise to remove the old sealant, wash the deck, and reseal for maximum protection.

Adding a second coat of stain to wood can even out the color to some extent, but it won't drastically alter the hue if the initial application is too light or too dark. It's more effective at enhancing the richness of the color rather than significantly changing it. Ensure the first coat is dry before applying the second.

When staining a deck, don’t skip surface prep, avoid staining damp or dirty boards, and don’t apply stain in extreme heat, cold, or wet conditions. Never overload the wood with a stain, as too much can cause tackiness or peeling. Also, don’t forget to test a small area first to ensure the color and finish look right.

Yes, it's a good idea to sand the wall with fine-grit sandpaper after spackling, especially if you plan on painting. You can do this by hand or using a sander, but the idea is to ensure the spackle is flush with the wall. Sanding will give your wall a smooth, uniform finish and help your paint and wallpaper stay put.