The back side of my instrument cluster was covered in a thick layer of dirt, dust, and mud dauber nests. A spray bottle of anything was just going to make mud. I worried about the soap and water option, given that the gauges aren't sealed. I didn't want the soapy water inside them.
I used a bowl about half filled with denatured alcohol and a clean medium paint brush. Paint brushes make great cleaning brushes and I have several of all sizes just for that purpose. The alcohol is a good solvent, it evaporates quickly, and it won't harm most electronics, plastics, or leave residue. You do have to be cautious with certain interior paints, inks, decals, and lettering, as it may remove or smear them.
I clean greasy parts, like bearings, with a large plastic bowl, a big paint brush, and mineral spirits. Works great. (Poor man's parts washer!)