It's my understanding that large museums and the Smithsonian have changed the ways that they care for coins. They now understand the damage they have done with the old practices. I can see how a new collector can learn from taking a brush or a pick at a low value problem coin. They can see the damage they are doing and be able to spot coins that have been worked on before they buy them. The hard part, the tough part, is learning what coins can be helped with proper cleaning and those coins that should be left alone. This is not something you learn overnight.