It may be that it's in the MM .NET 4.8 Dev Guide. We usually put instructions for upgrading in each Dev Guide, so you would need to go through each Dev Guide starting with the version you're moving from, through the version you're moving to. You can download the MM .NET 4.8 Dev Guide from the Downloads section of our web site. Here's a screenshot of the section I'm talking about:

Jeff, did you see the section in the topic "Moving Projects to MM .NET 4.8" on "Updating Windows Forms Applications" where it discusses changes you need to make to your Factory class?