Just done a flat which had peeling paint and distemper, it took seven days in stead of 4 been the max time, also it had crazing throughout so we embedded the render mesh in the skim, the customer swallowed the cost, but its horrible horrible thankless work, very repetitive, hard on your bones and muscles. You would need to cost almost double for the work or ask them to have it scraped, even then its normally only done half right..