A: I am staining a deck with it and it works great on the deck. Not shur if it works as well on a fence.
A: I used a Home Depot stain brand and cleaned the applicator with a mild soap and water.
A: Yes. Mineral spirits. Rubber gloves and a bit of squishing about, changing the solvent a few times. Then some soap and water if you want.
A: With my experience I doubt it can be washed for reuse and if you could I doubt it will still perform the same. The pads are made to be disposable. My advice would be toss it and replace.
A: Yes, absolutely, as answered above - soap and warm water will clean it to original white color, if you clean right after staining. It, however, will not last forever, since it does worn out.
A: Yes absolutely
A: Yes, but the material has to be thick enough not to run out of the pad. It could work with paint, but stain might run out before you can get it on the wall!
A: It may be used on smooth walls, but is more coarse than recommended. When the paint dried, it would not be as smooth a finish and could possibly have drips and runs. One would have to 'draw out' the paint so it would be smoothed out over the surface. A wall pad would do this on one stroke and would be faster, and smoother finishing that the deck pad.
A: If you’re staining walls then yes. If you’re painting, a roller would work much better.