When creating a new Action for a Method Directive, there's an option called synchronously invoke .NET method don't queue record nothing. Basically, a user generated dll's method must be selected in the method option. But first, the method dll must be copied into the Epicor Software\BPMServer\Actions folder on server and the BPM service must be restarted.
It may happen that after selecting the method in the .NET Action proxy builder, an error raises:
"Error retrieving action list from the server: Could not load file or assembly 'System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=...' or one of its dependencies."
The explanation seems to be that the custom project in Visual Studio must be built for the right .NET Framework version. In my case (Epicor 9 - version 9.05.604A) it was Framework 3.5. After rebuilding, everything worked fine.
