[Ros-release] Releasing an existing third-party package with…

I would like to release an existing third-party package that already
has some patches for ROS. (
https://github.com/PR2/pr2_ethercat_drivers/tree/master/eml )

I found the page on releasing third-party packages with Bloom (
http://ros.org/wiki/bloom/Tutorials/ReleaseThirdParty ), but it
doesn't discuss how to import existing patches from rosbuild, or how
to test the build with patches before I push it to the release farm.

Is this a sane thing to try to do?

Are there any more guides out there about doing this that I've missed?

Thanks,
-Austin