Can anyone share detailed approach to bidding complex development projects?

I’m terrible at bidding. I’ve tried to get advice and improve my estimating workflow for several years, and I suppose most of it falls in the “trade secret” bucket. Where I’d like to get to is a detailed, line-item estimate taken from client requirements / spec sheets. I’m thinking something that breaks an RFP into the constituent pieces – services, MVC triads, documentation, as small as I can reasonably breaks it, and from that I have some kind of guide to assign a budgeted hours to the task (instead of my blind guesses now, which are way wrong and probably too macro-view!).

How do you (accurately) estimate time for a development project from client RFPs / specs? Any advice on a starting point for estimates (hours per various tasks)?