Newbie could use some help-advice

I’m new to the power washing business and would like to ask for some advice. I’m a window cleaner that has been asked by one of my customers to power wash their home with aluminum siding so it can be prepped for painting. I’m thinking I should use my power washer and have someone after me use a scrub brush on a pole to clean the siding. Does this sound like the standard way of power washing or should I do it a different way? Any idea what I should charge for a 2 story home about 48’ long with an attached garage off the end?
Thanks for any advice…

I don’t know much about aluminum siding, but on most siding you don’t need to brush. Just spray your solution on with an x-jet or downstream, let dwell, then rinse off. Is the paint oxidized?