Nanking Blue paint for full HST set - how much will I need?

[jwpalfrey]

I’m having a dabble in repainting a HST set in to Midland Pullman livery. I have a Triang Midland Pullman and have sourced an old Lima HST set to have a bash at re-painting. I’ve never painted models but I’ve custom painted a motorcycle and re-sprayed a couple of cars so I’m used to a spray gun and fine masking. Anyway RailMatch seem to offer 15ml of paint in a pot, given I plan to do two power cars and mk3s which are mainly blue how much paint do you think I’ll need? 
 

And is there a better way to acquire the amount eg get a rattle can mixed up or order from an automotive paint supplier? I’m very familiar with automotive painting and re finishing but at model scale not so much. Hoping similar but working over I known paint/substrate on plastic isn’t ideal. However going for a satin finish is easier than gloss in terms of risk of contamination and reactions due to layering up wet paint.