I remember pre -V2 prayer books with prayers that clearly stated how many days of purgatory would be forgiven for each prayer.  These were Ukrainian Catholic (then called Greek Catholic) prayer books.  Did RCs have the same thing?  
I always thought that it was more than a little suspect that being rude to my mother, or fighting with my brother could be wiped out with just reading a short prayer, but, just in case .....  I did want to go to heaven, after all! :-)