cd $EPREFIX/usr/local/portage
git clone git://github.com/mslonina/mechanic-overlay.git
Add PORTDIR_OVERLAY to $EPREFIX/etc/portage/make.conf (full path must be used), i.e:
PORTDIR_OVERLAY='/Users/mariusz/GENTOO/usr/local/portage/mechanic-overlay'
emerge sci-misc/mechanic