To properly apply "White Walls", which is just the name given because of the oldest/most common colour to use, you need to shave a flat surface onto the tyre and then apply the paint to that.
This is usually done with a special tool that the pro's use, which has a wheel to spin the tyre and rim at a consistent pace, and the tool is placed a set distance away so a uniform finish is achieved.
Not sure how successful a DIY style job would be, based on the method needed.
not newcastle, have a mate that does it in Victoria in braeside, i think its about $120 all up for white walls so about $30 a wheel and i think an extra $5 or $10 for coloured.
anyone wants his number just p.m me, he does call outs, so will go to business's, homes, etc.