I'd allow a full day to do it properly, i.e. 8 hours.
Most of the job is in the cleaning and preparation/rub back, masking. At a minimum remove the caliper from the mount, remove the pads, and mask off all the slider boots and rotor etc for a neat job. Don't forget to mask off your 3/4 panels as well you'd be surprised how far the paint spray can travel!
