Just run a timed message in the channel asking people to move to the temp channel and then just sit there with that script until you're the last person there. Note that this can take weeks or even months to accomplish. In the future, if you're going to be offline for awhile, make sure you have some ops you can trust who will maintain ops there while you're gone.
Note that I'd recommend changing the script to include the channel name you're trying to get back instead of just # for all channels. It won't really hurt to have it for all channels, but you may not want to have it doing this in all of the channels you're in.
