You can use the spray cleaner while working from a ladder -- although scaffolding is better -- but practice at ground level first; the force of the spray against the house could knock you off a ladder if you're not careful. Some of these machines come with separate containers you can fill with cleaning solutions or anti-mildew solutions. Sprayers are so powerful that ordinarily you probably won't need to use a cleaning solution; if you do, remember to rinse the surface with clean water afterward.
basic formula? single color exterior labor only ranges from $0.85 to $0.95 per sq foot as a BASE starting point. Prices go up depending on multiple colors, slope of surrounding areas, multiple stories..etc.Some painters charge per window to mask off. Ive seen $25 a window to $50. Interiors without flooring can be factored the same way. When you start having to do multiple colors, cut ins, masking, room isolation...etc. the price jumps considerably. I always start with a base of $0.85 a sq foot and figure it out from there. the season plays a major role too. paint and materials are charged separatly and are typically marked up at a minimum of 15%. I always tell clients this. that way they pick the paint out they want and what quality they want as well. Anyways...thats your base. 1250 sq foot home @ .0.95 a ft = $1,187.50 (one color). Pressure washing, Add another $45-$55 per hour. a 1250 sq ft home is not going to take longer than 2-3 hours if its a single story.
If you are going to hire a contractor (professional painter) give a room by room punch list of the fixing of holes small or big, have it identified for the painter to tell you if you need a drywall finisher or if he does this type of work good. Wall repairs can be 3-5 steps to do repairs ( one per day for good drying of patching material and a good sanding) this is what gives you a good paint job only using high quality paint.