recoating a metal roof?

[varmint]

We have taken the plunge and commited to getting a solar PV system installed on a small barn that is well situated for it. We hope to generate most of the power we use in our home on an annual basis. The barn's roof is a simple gable, 5/12 pitch, pretty low to the ground. The material is painted corrugated aluminum, and my question is the best way to clean and refinish it before the solar panels get installed. The old finish is chalky and quite faded. My plan, at present, is to get it pressure washed clean, and spray on a white elastomeric water based roof paint. It's corrugations are too deep for rollering. The issue is finding an airless sprayer that will handle this coating. The requirements for the two products I am considering (Calbar and Uniflex- leaning towards the Uniflex) are basically the same: the sprayer needs to develop 2800psi, with a spray tip that's .033"- pretty big. I think I can rent one, but none of the painters I know have such a serious sprayer.
Has anyone got any experience with such a project?? This is outside of my normal undertakings, but seems pretty doable. Weather is my biggest worry.