A lot of times you’ll want to emerge a masked package (or a masked version of one). One short way to do this is ACCEPT_KEYWORDS="~x86" emerge package (replace x86 with your architecture). A slightly shorter way is to create a file called /usr/sbin/expmerge with the following contents:
#!/bin/sh
ACCEPT_KEYWORDS="~x86" emerge $*
Then just expmerge package
Mixing unstable with stable packages can lead to problems, so it’s recommended you pick one type and use it all the time. This is more important for libraries rather then programs.
NOTE: the aforementioned method of emerging masked packages is deprecated and unsupported. please use /etc/portage/ (man portage, man emerge) This is used by:
echo "package-category/package-name" >> /etc/portage/package.keywords