Estimating Systems?

Alright, I know I am taking a risk by posting this because I know everyone just loves the "how do I estimate" questions. However, I am going to ask this anyhow. I understand that every contractor has a different overhead, profit, production rates etc. Of course every job differs as well. Lord knows the market varies by geographic location among other variables. I am new to estimating. I have a question for the more experienced guys out there. Do you have a specific system you use to calculate your estimates with your company's figures? (IE overhead profit etc etc) I know alot of people go by the sq ft. I picked up the 2008 cost estimator book and it seems like a relatively solid system for bidding but I am sure not everyone uses that method and have their own formulas for calculating their numbers. I was hoping perhaps some of you guys would be willing share your methods. Or if anyone knows of another program or book out there. There is no "one size fits all" method for estimating, per se, but I kind of wanted to try on a few for size against the one's I have already used. Any other useful tips for estimating are welcome. By the way, as of right now I am mostly doing repaints if that helps you answer the question. Thanks!!!