The Bitcoin Core PR review club site links to this beginner's guide to IRC.
There are more impressive IRC setups such as Pieter Wuille's setup.
My setup is: juicessh on my phone, ssh into my VPS (non-tor), where I run irssi in screen, which connects via tor to freenode and other networks
But you said you wanted to minimize setup time. In that case I would ...
On Ubuntu, I like weechat.
On OSX I've used Colloquy before but have recently upgraded to Textual which is not free -- unless you build it from source :-).
There is even a web interface for freenode, but I'm not sure if it requires authentication to join the channel.