Our barn roof is Onduline, a/k/a Onadine, an asphalt composition (organic fiber is embedded and the material is pressed so it is corrugated, looking like a corrugated steel roof). The coating is almost off and I want to get some more use from the roof. It is steep so it does not stay wet and seems to still have it’s integrity. I have been told to power spray it and then put on a high grade 100% acrylic. This will require the use of a lift, I suppose. Thanks.
Don't use a standard house paint. It will peel off in just a few months. I'm thinking that a roofing mastic would be better. Something like Sno Roof.
Power washing the roof is a great idea to remove the dirt and dust. Be careful, the roof will be slippery.
Spraying is a good method for application. Plan on two coats from two different directions or sides. It will be difficult to get all edges at one time. Using a lift is optional if the roof can support your weight.
Spraying a mastic coating will require a powerful gas powered airless sprayer, a large tip (min. 525) and 3/8 inch airless hose.