How do I wash a large section of the wall?

Hi Denise, Just use a power washer or hose with car wash brush on.

If you wash your interior wall, use a spung mop on a handle and product of choice, my product of choice is “simple green”.

I was thinking you meant interior walls. If that's the case, you can use a swiffer-type mop with a rag attached rather than the commercial products Swiffer sells. You should make a weak solution of water and tsp. Wash from the bottom up, so that dirt drips don't make it worse. Then rinse with clear water using a new mop head.

Inside or outside? If interior walls I use a swiffer type mop and a vinegar water solution. Outside, I just use a garden hose.

I would rent a pressure washer over the weekend and get it done easily and quickly. They do not rent for a lot and do a great job. Just follow the instructions.