There is Model Master Acryl which is supposed to be thin enough to airbrush, but it goes on bumpy. I stick as much Tamiya thinner as I can fit in those jars when they're new, and I sometimes still add more thinner once it's in the airbrush.
You don't really have to be spending time thinning. However much unthinned paint you put in, put in a "good bit less" thinner & slosh it around with the pipette or eyedropper. It's not critical enough to have to be done so carefully.