It couldn't possibly be easier or faster to ask here than to Google this. Here.
>what plugins are available for a particular package?
yum list package
>How do I check repositories for updates
yum check-update
>and how do I update cached information?
yum makecache
There's always the yum project documentation, or the RHEL System Administrator's Guide, but if you really want to get into the details you may also want to look at how RPM itself works.
Figured it out! yum-cron does indeed sleep a random time to reduce bandwidth load. I commented this out and it ran immediately.
577 # Sleep a random time 578 self.randomSleep(self.opts.random_sleep)
fpm makes it easy to build .rpm and .deb packages. You can then either just distribute the .deb and .rpm files or host an APT repository for the .deb's with aptly and host a yum repository for the .rpm's with createrepo.
If you are only interested in packages corresponding to the version of the distribution installed, try:
$ yum provides '*Xmu/Atoms.h'
See the yum wiki
Otherwise you can use repoquery to find matching packages in other versions of the distribution