Pitching startups on technical writing

I've been a technical writer for startups--recently at Realm, before that at RethinkDB--and I'm thinking about trying to make a go of documentation consulting in the new year. I think this is something a lot of startups, particularly in the developer tools space, could use. Many of them don't have enough work to hire a full-time technical writer, but they still need docs. I've worked at startups and small companies as a developer, too, and I know that even when everyone agrees in theory that docs are important, in practice they tend to remain in "minimum viable" shape indefinitely.

So here's my dilemma: I don't know how to pitch this. There are probably a few people I can talk to about leads (and I'll likely be doing that after the holidays), but I'm not sure how to approach folks I have no relationship with. I'm aware that to some degree this question is more "How do consult," but I have a definite sense that it's a lot easier to pitch yourself as a JavaScript, Rails or even (gasp) PHP dev than it is as a docs writer: it's hard not to notice, for example, that when HN does its monthly "Who's hiring?" posts, it's rare to see anyone looking for tech writers--even companies building APIs, where the documentation is arguably the user interface.

If you're a tech writer yourself, do you have any experience with this? And if you're not a tech writer, how do you think a pitch like this could work?