Patching and Plastering - Skimming versus Patching

I have plaster walls and ceilings with many thin cracks all over it. We tried scraping the ceilings and some of it scraped easily, other parts are left unscraped because it's too hard. We had a painter tell us that skimming the walls and ceilings would cover up the cracks and unscraped parts, and basically make it seem like a new wall. Will the cracks eventually seep through again? What does the process of skimming involve, is it just putting a new plaster coat on? Thanks

If the cause of the cracks is not fixed, the cracks will eventually reflect through the skim coat. Rout out the larger cracks to get a good key for patch material. You may want to use tape over the larger cracks.