If your co-founder is more socially adept observe them and watch what they do. Ask them questions, be up front, maybe they can offer what they think is trivial, but for you pivotal advice.
One thing that always works for me is to ask "can you explain to me" type questions specific to that persons profession or interest. If it's a model ask about what it's like to be a model, do they like any specific work over another, how'd they get into the buisnes etc... there are hundreds of little questions about any profession/topic that I'm genuinely interested in knowing the answer to. About that one topic they know more than you, let them educate you.
In terms of improving meeting with "photographers, models and the general hipster crowd", does it help any if you think of them as "people"..?
What do you define as "utterly painful" and "social ineptitude" in your case?
What do you say to yourself as you enter these sorts of situations? Is it "Wow, I suck" or "Wow, I'm awesome and have something that's really of value to these people, I should find out what they're looking for and demonstrate how I can help them"?
I know the whole self-talk thing seems bogus but I think it does have an impact.
Well I acknowledge they are certainly people :) I've suffered through a few years of depression which include being medicated. I suppose I'm just terrible at initiating and continuing a conversation. Entering a conversation, I typically feel insecure so this is leaning towards more of a "Wow, I suck".
I realize such thoughts are a terrible handicap in networking situations and I'm working on improving that.
There is no magic bullet so that's actually a pretty good approach to improving things. :) It just takes time...
It can seem fake to try to take the positive angle but it's important to try. When you have the choice between choosing to think of yourself as awesome or not, try to always choose the awesome option--even if you don't really believe it...
Also, if someone ever tries to compliment you on something, make sure you don't try to deflect it--just say "Thank you" with a smile.
Yeah, it all sounds a bit wanky but I've found it helpful for me. :)
(Also, check out Bar Camp Auckland http://twitter.com/#!/barcampauckland if you've not been before--there's some good peeps involved.)
Good luck!