Recently during an end of tenancy clean for a local estate agent, we had trouble cleaning the interior walls of a property that were painted a neutral colour with emulsion paint. The marks were everything from drink spills, to fingerprints, makeup and everything in between!
We tried many products, from multipurpose, to multipurpose with bleach and a scourer. We had one cleaning block left (one of the preloaded blocks from that well known brand beginning with F) and couldnt get any more in time.
We did however, find a great compromise - we used sugar soap! It did a great job on most stains with a microfibre cloth and a squirt straight from the bottle, and it didnt damage the paint. Some areas that were more inground needed a bit of persuasion with a scourer and that required care not to damage the paint, but it did the job brilliantly.
Letting agent? - see more about us on https://www.totalblockservices.uk We can provide references from others