Welcome Carl.
The best best advice I could give on how to estimate is to break the job down into small sections. Ie if you have a whole interior house to do then list out every room, break it down even further by listing out ceiling, walls and trim separately. Go through each one and asses a time required for you to do it. Then go and add on how much paint for each task. If you dont know how much time it will take or how much paint it would take then you are probably in the wrong forum. Once you have your total hours (include setup and clean up each day) multiply the hours by your hourly rate you intend to charge, it should be what you want to make per hour plus something extra for the business 20% to 100% markup, again this will be geographically specific. Take your materials and multiply them by the charge rate per gallon, if you pay $20 a gallon (including tax) maybe you want to charge $30, $35, $40 plus, its up to you. Dont forget if you have to pickup the paint you need to charge for your time there too. Whats left? Daily costs like gas for vehicle to job, milage for vehicle to job, insurance, workers comp, misc expenses like fillers, rollers, tarps etc. What about ladders, sprayers, or any other equipment. You should be charging for them too, the amount you charge is up to you but you could start at the high end with the cost it would be to rent the equipment.
When you are all done with your costing sheet you can go back and calculate the cost to do the job including an hourly rate for you and see what profit the business will make to see if it is a worthwhile venture. The business profit will essentially be paying you when you go to do any un billable activities such as doing a quotation, following up, typing proposals etc.
Good luck
hello, a little about me, I was a residental painter for about four years, currently I am a fulltime firefighter, just started my own res. painting company. I am lucky to be able to live and save just on my firefighter pay. ( I am a simple man ) I do "good" work and I am fair and honest. The questions that I have are not so much the painting part but the business part. How to estimate, how to advertise, do I need an accountant or lawyer. mostly the estimating part. I have read the other posts on estimating, like knowing your overhead, cost, labor and profits etc.. Any help would be great, including help with this site. 
