Need something, one or two galons. That I can pump up and rinse dust out of equipment. Compressed air doesn't clean well enough. Gotta be water. The garden sprayers from the store are the right idea. But, the new ones with the plastic wand just don't have the flow.
Years ago, I used a kiddy toy fire extinguisher, and that worked reasonably well. But, it's only about 20 ounces, and only lasts for one quick squirt.
Best I've found have been the Roundup sprayers, with the brass wand and pump top. A pressurized water fire extinguisher would do a nice job, but would look a bit strange.