I wouldn't say you'll use IRC directly to promote. It's just another communication channel with people. Think of like twitter, everyone is almost always online thanks to bouncers or irssi+ssh setups and you can query whoever you want or need. They may respond if they see your message and think it deserves an answer.
I'd say most of its interest comes from the support channels like #rubyonrails or #python where you basically help people. After a while, you get to know regular users and thus making new connections or even friendships. As an example, I've got friends hanging out in a french sys-admin related channel who sent to me people looking for python training. I made an offer and we later called to them to finalize the order. I'd say such things are a consequence of your genuine participation in channels rather an objective in itself.
I use quassel as an IRC client, the core is installed on my personal server, being always connected. I connect from my home or my laptop and always get only what I haven't read thanks to quassel acting a bit like IMAP. I also have a bitlbee setuped in order to act as a gateway to gtalk and hipchat, meaning I got every single possible chat protocol I may use in quassel.
I desactivated notifications, which means If I minimize quassel, I won't see anything, letting me focused. After each focused work cycle ( like every 30-45 minutes ) I just check if anything happened there and answers depending its importance and my current priorities. I don't say I'm not available, which may lead in a debate on why I can't answer right know, I just don't answer back until I got prioritized stuff done first.
This way I can handle chat with wrecking daily productivity. As opposed to that, phone just trouble my productivity, I almost never answer on my phone except for a few people and use almost exclusively chat to avoid that.
