National Estimator will not help for flat rate pricing on service work.
Flat rate will work for you and a apprentice. You must know your bottom line and never have a ratio greater than 32% between payroll and gross income.
Establish what it would cost your company to install a GFCI outlet on the outside of a residance using rx and 55 feet from the loadcenter. Take that cost and add 65%. There is your flat rate for this instalation for your company. Now make up a spread sheet of most common jobs and put a price next to them. Carry this sheet with you when you go to do a job and use it to give your customer a price before you start the job. As soon as someone calls you they are your customer you just have to make sure they stay your customer.
Of course it's more complicated than that but this is a general idea.
Bill
