Troubles getting a nice finish with gloss paints

You need to airbrush a light mist coat before applying your color coats. This has been described in FSM countless times so you can probably find out the exact way, I don't really paint gloss that much but I do know that is most likely your problem. Or you're airbrushing at too high of pressure so the paint is semi-dry by the tiem it hits the surface, not usually a problem with gloss paint though.

Getting a good gloss surface is a challenge, especially with acrylic paints. This is one area where enamels and lacquers kick acrylic butt! But even then getting a "showroom" shine is difficult. I know most of the car guys will paint, sand, paint, sand, paint and polish, polish, polish before being happy with the surface.

Have you tried adding Future to your paints? It has the twin benefits of smoothing out the paint flow and increasing the gloss level. Spraying a top coat of Future will also help in filling in the rough spots as it self levels beautifully. 

Oh come on now... leave the future for the floors! J/K

Max, what the problem is - the paint is drying before it can settle onto the object.
Yes enamels can do that too, just like acyrlics. Some enamels are fast drying and then when you thin them out more they can dry even quicker especially when finely atomized from an airbrush.

Not knowing your specifics on how you mixed the paint (ratio), air pressure, spraying distance, humidity, temperature, etc... I'll give a few basics to look out for and what can have the most effect on the rough sandpaper like finish.

• Paint thinned too much
• Too high of air pressure
• Spraying too far from the subject
• Temperature too high (unlikely though)
• Must spray a "light" mist coat first
• The color coat must be "wet", just shy of dripping

A mist coat is just a very light coat of the final color paint sprayed on so it is almost transparent. While it is slightly "tacky" that is when you spray your wet color coat. The purpose of the mist coat is to adhere to the surface and give the next layer of paint something to hold on to. As far as spraying the color coat just shy of dripping, you can spray it in layers. Just as a layer gets tacky, spray again. It's worked for me for many years even when I was using spray cans. It took me awhile to get the hang of an airbrush. I was used to cans for models and big spray guns for cars. Once you get the combination somewhat worked out it will flow with ease from then on.

 

Jim's covered the basics—now here's a sneaky devil to watch out for:

If your paint is a little too thin, or if the temperature is too high, or if you are using a highly volatile solvent as your reducer, the painted surface can be chilled by solvent evaporation. This will produce the mottled effect you describe. The effect is worst with aerosol cans, but you can do it with an airbrush. Glosses are the most vulnerable, but I've managed to do this with a flat.

I suggest practising on a piece of scrap or a paint hulk until you feel you have control of all the variables Jim mentions.