Is there a link to the scratch solution and how to set up?
I'm not sure what you mean by "the scratch solution." It's really pretty simple: configure Scrivener's Scratch Pad to put its files in a location accessible by your Android editor.
In Mac Scrivener 3, the location is defined in the Scrivener -> Preferences -> General -> Scratch Pad tab. In Mac Scrivener 2, it's the Scrivener -> Preferences -> General pane. In Windows Scrivener, it's Tools -> Options -> General.