Primer from a can

OK......I figured out that I sprayed lightly and quickly to avoid any runs with the primer. There's gonna be a learning curve in the future. Thanks for the response.

Many folks use Tamiya white primer when air brushing, but it requires a lacquer thinner, so you must have adequate ventilation.  There are other options, but most I have heard of are lacquer-based.  I have not had great luck finding acrylic primers, but Vallejo makes some.  I intend to order some one of these days to give it a try.

As Don mentioned, wet sanding will make a big difference.

Does it have to be from a can or is an airbrush primer an option?

Almost all primers I know, except stuff made specifically for modeling, tend to be a bit  rough.  Normal procedure is to sand surface with fine sandpaper, say #600, to prepare it for gloss or semi-matt surface.  However, the thicker (wetter) you spray it on, the less rough it is.  Excessive roughness is a result of too dry an application, as in  too great a distance or moving too rapidly.