If your only options for interacting with a technical, sysadmin-/developer-focused project's community are these, which would you go with?

Boosts appreciated 🔄

1: an XMPP MUC that requires you to have an account on some XMPP server

2: an IRC channel that requires enough knowledge of IRC to join the channel

3: a mailing list that requires an email account and rejects HTML email

4: a ticket tracker that you can interact with from either your email address (rejects HTML email) or from the web UI but the web UI maybe requires creating a new account

5: none of the above (just don't interact with the community)

You own a small company with one employee (you)

Clients wants company to take on a big project, they describe what they're looking for, you give ballpark "won't be less than this" estimate, and they're happy to pay whatever you charge, so you agree

Now you have to start planning things out.

You mention the possibility of helping to a friend, he expresses interest, and knowing that he's a better programmer and his experience would be very valuable, you add him on and decide to work on it as a pair.

But what software dev process do you use? Hack at it till it works? Test-driven development? Feature-driven? Spiral? RAD? XP? Waterfall?

(I am asking for advice)