I'm happy to share that releasing a platform just got a lot easier!
I got rid of a number of manual steps in the process and releasing artifacts is now done entirely by CI. You do not have to checkout code and run a single build locally nor you have to deploy artifacts to sourceforge. It all happens automatically by triggering just two CI builds (one for core and one for platform).
See updated instructions at https://wiki.openmrs.org/display/docs/OpenMRS+Platform+Release+Process#OpenMRSPlatformReleaseProcess-MaintenanceRelease
1) Apply the config to other branches, because currently it's done just for Platform 2.x and update wiki for other types of releases.
2) Apply the same to the Reference Application release process.
3) Create the release notes page automatically (script finding db diffs, committers, issues).
5) Add integration tests for platform (only Reference Application is currently covered by UI tests).
Thanks @cintiadr for your quick help with the sourceforge issue!