Getting a Smooth Finish When Painting Interior Doors

Spray paint. Sand smooth first. Use Light coats that fall off the edge. You'll get drips if you don't paint off the edge. Let dry and recoat. We primed then painted with RustOleum(r) for metal on our wood cabinets. It looked fabulous.

I've painted many doors, both interior and exterior, in my time and found in order to have as close to the smooth finish you're seeking is to sand the doors first so they have a more porous surface to accept the paint. There's no guarantee it will work for all surfaces but you can try it on a small portion first to find out.