I think it comes in both varieties, a foam in a pressure can and a liquid spray in a bottle sprayer.
Difficult?? Apart from the height of my 5th wheel ceilings, it is not difficult, labour intensive maybe, but not difficult. If it is just dusty, a vacuum cleaner works fine. I guess it depends on how it got that "dirty". Those water stains are not easily removed and require a delicate touch, a few light applications, light rubbing in using towelling, then blotting and drying in between applications.