Try adjusting the thumbscrew on the regulator cap that screws onto the air can. Turning it clockwise will give you more pressure and prevent "dotting".
When I airbrush from my air can, I screw on the regulator cap, then I hold the trigger down (without a jar attached to the handle) and turn the thumbscrew on the cap clockwise until I get a good airflow coming out of the gun. While holding the trigger down, you can turn the thumbscrew both ways to see if the airflow is powerful enough.
Once you settle on where to put the thumbscrew, then adjust the needle tip connected to the siphon tube coming out of the jar (and your paint). Start by screwing it all the way down (clockwise), hold the trigger down, aim it at some scrap cardboard or something, then back it off (counterclockwise) until the gun sprays and until the pattern is what you're looking for.
I initially tried spraying Liquitex (Grumbacher) acrylic paint in my brush the day I bought it. It did EXACTLY what yours is doing now. I thought the paint was too thick, so I added a bit of water. Well, it sprayed. THEN the paint ran off my armor! After trial and error, I discovered that the paint consistency was FINE. It was my air pressure that was the problem. After figuring out how to set the regulator, I was in business!
I've sprayed acrylics, enamels, varnish, lacquer... you name it! And I've NEVER had to thin/water down ANY of them!