1. Install this plugin. Create a folder and extract that zipfile.
2. Use gimptool. As for this time of writing, in Linux Mint Maya 13 (based on Ubuntu 12.04 LTS), I need to install libgimp2.0-dev.
gimptool-2.0 --install-script lomo-gimp.scm
3. Launch Gimp. Go to Filters->Artistics->Lomo Gimp
4. Alter whatever variable that you need.