This describes how to access files and directories on the Android OS that are usually not accessible with a file explorer. All my machines are running OSX so these instructions should work similarly for *nix derivatives. Windows users will require a bit more research on their own. A lot of assumptions are made, so if you require clarification on anything, ask and I'll do my best to answer and update this gist.
You are going to need adb and fastboot commands, you can either install
Android Studio
or get just the SDK.
I suggest just getting the SKD tools because it is a much smaller payload and
has everything that you need.
Unzip/Extract the contents of the SKD directory
Execute the android command in the tools directory, it will start the SDK
Manager. Uncheck all boxes except the "Android SDK Platform-tools" and click
"Install packages...", accept the terms and let the installer run. Close it
when it's finished and check the platform-tools directory, it should now
contain, among others, the adb and fastboot commands. If you know how to
add the commands to your PATH, that will make things a little bit easier but
it's not absolutely necessary.
TeamWin aka TWRP is my custom recovery of choice but you
can use whatever you're comfortable with. Search for your device and follow the
instructions to install the appropriate version. I prefer getting a direct
download. Take note of where it is saved, this will be the
/path/to/recovery.img I will refer to later.
Connect your Android device to your computer and run ./adb devices from the
"platform-tools" directory, your device should be listed.
Run,
./adb reboot-bootloader
and wait for your device to load the bootloader, then run,
```./fastboot boot /path/to/recovery.img````
The above commands should load the custom recovery. TWRP and any other custom recovery should have a file explorer/explorer, use that to find and copy and the directory or file you need to a location that is accessible by a regular file explorer.