My go to paint is Vallejo Model air as the colours are always chipset accurate and not "scale correct" of most other brands. I don't usually thin these paints, but occasionally I will depending on the colour. The darker the paint a little thinner is needed. I will use with bot gstandard tap water or their flow improver.
However, I will use others depending on needs and so, for Japanese aircraft where Aotake is needed I use Tamiya X-13 which is the best rendition of this colour and is always applied by paintbrush (Tamiya doesn't go through airbrush well unless really thinned!). Originally, this paint was always hand made and applied by paintbrush, so I am using the original application method!!
Clear paints for lights (red, blue, green, yellow, orange) is Tamiya and always applied by paintbrush. If painting onto clear parts then just apply but onto normal plastic parts then I will put a base coat of white aluminium down and with the clear colour on top makes it look like a bulb.
When it comes to metalics I use either AK Xtreme Metal or Vallejo Metal Color. Both spray fantastically with no thinning. If I need tt paintbrush a metallic then Vallejo Model Air metals from their range is used as they tend to be a little thicker and so more paintbrush amenable.
There are colour crossovers betweed AK Xtreme Metal and Vallejo Metal Colour, but the shades are different and so you can use them together on the same model to show replacement panels etc. Neither range, despite the official blurb likes being masked or handled and so I always put AK Internediate Gauzy Agent Shine Enhancer over them as a protection before continuing. THis can be sprayed and turns totally clear on application. It can also be paintbrushed too!
I am tempted to try Molotow liquid Chrome, but until I know what I can use to clean my airbrush then the refill bottle stays closed!
I am not averse to use any paint brand if I need it, but I always do my colour research very carefully and stick to original accurate colours as the scales I work with are 1/35, 1/32, 1/24, 1/16.
I am just waiting for some Lifecolor to turn up as I noticed a colour that will be useful for some of my Panzer interior builds and want to try it and sacrifice a spoon to the great white paint god!
James