Claude can write a full proposal or quote from the information you give it. You don't need to start from a template. You just need to tell Claude what the job is, who it's for, what's included, and what it costs.
A prompt that works well: 'I run a residential painting company. I've just quoted a client named the Hendersons for exterior painting of their two-storey home. The quote is $4,200 and includes two coats, all prep work, and a 2-year touch-up guarantee. Write a professional one-page proposal I can email to them.' Claude writes it.
You can then refine it: 'Add a section about our process,' 'make the tone warmer,' 'include a line about what's not covered.' Each revision takes seconds.
Once you have a proposal you like, save it as a template. Next time, you give Claude the new client details and ask it to fill in the same structure. You'll have a consistent, professional proposal ready in under five minutes.