This overlay contains some packages that I needed at least once, so I am sharing them here just in case someone else needs them.
To add this overlay just edit /etc/layman/layman.cfg and add the following url to the overlays value https://raw.github.com/lonewolf4/gentoo-overlay/master/profiles/repo.xml
Example:
overlays : http://www.gentoo.org/proj/en/overlays/repositories.xml
https://raw.github.com/nelsongraca/gentoo-overlay/master/profiles/repo.xml
Then just add it with layman -a ng