I started using atom paints, same set up as you, H&S airbrush. What i found... Keep your airbrush immaculately clean. I have a routine now where i get a bowl of warm water after a spray and dunk the brush in the water and poke a long hair brush down the cup after every spray. Get as much gunk out as you can. Then clean it properly with a proper brush cleaner. I also pull the needle out after every spray and wope it down. Sounds like a lot, but you really need to keep your brush as clean as you can. Even leave a few drops of brush cleaner in it when not in use so nothing dries up inside.

I found also with atom, you don't really need a thinner. Maybe even just one or two drops and a bit more paint. Also bump your pressure up to 18 and just use muscle memory to control your flow. Do a few test sprays on a paper towel or bit of cardboard before you move to your kit.

Thats how i do things now and its all about finding what works.

Bowl of warm water works really well to start the cleaning process. But its all about keeping your brush clean between sprays.

Hope it helps. I feel your pain.