Rob:
Just curious, what brand of paint is that you have shown?
I use a local brand here in the US, Model Shipways acrylic flats.
It goes on very smooth, is easy to work with and can be diluted with water, has no offensive smells and coats very, very well.
I have seen but not yet tried using what is called Japan Colors which is a very fine grained tube acrylic used, I believe, in acrylic art painting. When working on wooden ship models it is excellent, covers well, etc., but is a tube product so come out thick and is again diluted with water to the consistency required. I imagine it would be great for card models too, as long as you are careful in applying it sparingly and not too heavy to have the water soak the card. Best thing is they come in a variety of colors not offered in most other mediums except for oil paints.
I haven't tried the MS paints using a spray gun yet, but I am told it works great that way too! I haven't had the need to apply the paint over any great areas yet, using them to simply touch up folds, edges and the like.
Oh, yeah, I also like using it to make railings and the like, although in a previous thread I mentioned how it requires a few coats to adhere the threads together for railings, but it work great and is easy to apply to avoid blotches and globs on the joints since water will thin out those unwanted and unsightly spots. I use a very thin brush for most of my painting needs, one brush in fact, although there is a whole slew of them in my tool box if needed. I just need to control those gorilla hands in applying the paint! Ah, but then the mistakes can be removed fairly well with water and a Q-tip or even the cleaned brush, if you do it quickly before the paint dries.
Just some rambling thoughts...
Jim