Mr. wbassett has collected a lot of information on various paint brands and how neutral they are. He may be able to point the folks in Australia towards a local brand that suitable as a screen paint.
If wbassett can even just identify an Australian brand that is close to a neutral tint, I may be able to suggest a tweak to make it closer, given the tint formula. Not very scientific but I have managed to get close by eye when developing the custom tints so at least it would be reasonable.
I know of a fellow screen paint experimenter who is in Australia that may be able to help with measuring samples if you would like to pursue this further. I can provide some details on how I went about making up many tint variations without spending a fortune at the paint store.
In my other stomping ground we are currently exploring the accuracy and validity of various measurements such as RGB values for D65 and spectral reflectance response curves. When these discussions have reached some conclusions I will be able to validate my custom tints. At that time I could be persuaded to send some samples to one or two interested members in Australia. These samples could then be use to do visual comparisons and to train your eye to recognize a neutral or balanced gray when you see it. Alternately wbassett may be able to send you a painted sample of Sherwin Williams “Gray Screen” or True Value “Winter Mountain”. These to proprietary tints could also serve as good visual references as to what a neutral gray looks like.
I'll poke Mr. wbassett and see if he will drop in and comment on this possibility.
