Ask HN: Developers, how do you estimate projects and write proposals?

I’m interested to know how fellow software developers (freelancers, small businesses) estimate projects for clients.

Do you use any tools to come up with a quote? Do you send a proposal document to clients? If so, do you use a tool to generate one, or do you just use a template in a word processor? What are your main pain points when quoting for work?

Cheers!