Aerosols.
The only surface that you might find tends to reject aerosol paint is on road
signs. This is mainly because most painting is carried out at night, which
is also the time when the maximum build up of condensation occurs!
You can easily remove condensation from almost all surfaces by using a window cleaner's rubber wipe. You can use these on their own or attached to an extending pole.
The fastest method of reaching the back of road signs is simply to climb up them! You might be a little surprised at how big some of these are when you get up close, but don't be daunted, as they are quite easy to climb. You might like to carry a large sling bag or something similar to carry your wipe and paint whilst you climb, or attach them to your body using a belt or some string.
As you work you will think passing
car headlights are illuminating you; they are, but very few drivers will actually
observe you, and even fewer are likely to stop! If someone does stop they
will be on the opposite side of the road, and you should have enough time
to make yourself scarce! You can come back another time and finish the job.