Part of the problem with the spotting,sputtering of paint is dirty nozzles and lager pigment in the paint. All of the previous mentioned methods help some times. But having used rattle cans for years painting magic and clown props. after turning the can upside down, and spraying to clear when the can is empty. I have a parts drawer in one of the small multi drawer units that I put all the working spray heads in. Then if you have a bad one you can always change it out
This has saved me many times when the nozzle or the lift tube gets clogged on a new can. There are a number of styles of spray heads stemmed ones, ones that slip over a tube in the top of the can and ones that have a removable pattern nozzle in the spray head so you can spray vertical or horizontal with wide coverage and not have to tilt the can.
Not that it would been much use on ship models, But if you are looking for mud spatter, or multi colored paint splatter and spots of paint effect. Say on deck cargo, you can take a # 11 type exacto blade (hobby knife) and score a line across the nozzle opening. Will give you a one type of pattern, more scores and at different angles will give different patterns.