Updating portage tree
Make sure to include version numbers and any specific USE flags that you think are needed/unneeded.
This may not get you your package right away, but it will get you and others the package.
It is recommended that you pick one or the other for maintaining your system.
As every package on Sabayon comes from either Gentoo proper or from Sabayon's Gentoo overlay, using Portage is generally considered unnecessary, there are of course always corner cases.
If you are going to mix and match, ALWAYS use Entropy to upgrade portage.
Add each package there with the USE flags that you want it to have, including the -USE flags for the flags you don't want it to have that may get added by the If your package or USE flags requires new dependencies with specific settings, you will need to add those in here as well. It is best to use Entropy to meet all dependencies for any package, prior to emerging the actual package.
Sometimes an app is missing from Entropy and the Portage Tree but is in an overlay.
In this scenario it's helpful to install what you can through Entropy and only install the missing components from the Portage Tree or an overlay.
In the case that is a folder, you can edit the file /etc/portage/package.use/00-sabayon.package.use/00-sabayon.package.use, or create another file like 01inside that folder.
Following these rules can make mixing and matching between Entropy and Portage safer, not safe, just safer.
With these rules you will have not only a history of what you have done, but a pretty good idea of what needs to get undone if your system becomes unstable or unusable.
This reference is not meant to be complete or authoritative, it's a crash course.
Only daily necessary skills with Portage will be discussed, the See Also section has links to more information.