Do you remember textured ceilings? That stuff was pretty thick, so the nozzles may be close to what you need. This is gelatin, and if you heat/thin it enough to get through a small nozzle, it may take many coats to build up enough. A deep fuzzy roller may be a better, if lower tech method.
Let us know how it goes, David
This is a great idea, the only thing that worries me is that these guns look like they all got a metal nozzle. Did someone ever got liquid emulsion in contact with metal? Did it get terribly ruined?