There are just a few essential things you have to know to create a beautiful finish, like oil and water don’t mix. The finisher can work with many variables and a good finish is assured when the variables are in sync. The finisher can control the viscosity of the coating, the psi, (if you are using a conversion gun or a variable speed turbine,) and the size of the needle and nozzle. Needles and nozzles however, must match. A 2 mm needle works with a 2mm nozzle, etc.
Coatings companies as well as equipment manufactures offer guidelines for choosing the right needle and nozzle. A larger needle and nozzle is recommended for higher viscosity coatings, such as latex paint, while smaller sizes work with thinner materials, like stain. It is always surprising however, to discover that a finisher achieved a gorgeous finish while breaking all the recommendations regarding viscosity, pressure and needle and nozzle sizes. That’s why woodworkers are artists, who sometimes bend the rules and produce amazing results!