Many thanks to Admiral Drax for supplying the notion that whilst thinning might be giving me ultimate control over the amount of paint applied, nonetheless actually having enough pigment means one can see what one is spraying and hence spend more time painting and less time faffing about trying to correct things are not wrong, just not what I thought I should be seeing.
Incidently, I still put a few drops of thinner in the resevoir first, as this prevents any 'lumpy' paint clogging the airbrush up.
*No. (I may be continuously improving (not hard, considering the starting position), but am not registered. Nor have I written myself a quality manual. That would be sad, shame on you for thinking it.)