Agree with a magic sponge or magic eraser. Google either of these phrases and it will show in Amazon or eBay etc. They are not always sold in supermarkets (well I can never find them!)
Home Bargains stock them I think. It will remove marks such as scuffs etc. Also great for getting rid of tea/coffee stains from mugs (if you don't have a dishwasher). Very handy to have some as they work really well cleaning marks from stuff.
If you use a damp microfibre, lights and sunlight will show where you have scrubbed - it will look horrible in a certain light. Had this issue myself so had to redo the whole wall.