Most white paint is heavy with zinc and or titanium (not sure about acrylics?) and this makes it semi-transparent and pretty hard to brush. It can be a pain to spray, too.
I usually mist white on with an airbrush in lotsa light (very light) coats. With a brush I undercoat with a VERY light grey - not the usual mid-grey primer.
Gloss white is the worst offenfer. I don't use it. Satin varnish afterwards. Gloss varnish if you really have to
Never tried it, but I have a hunch that Tamiya flat base in acrylic whites would help.
Cheers, Andy