S-3 Viking painted

Today I got the model painted totally, all it needs next is a coat of gloss varnish ready for the decalling and weathering;

After spraying the model with Mr Hobby H308 (FS 36375) it was lightened with white and sprayed with a random mottle pattern in between the panel lines. The two panels behind the cockpit were sprayed with H307 (FS36320) and the gear bays and wing fold insides sprayed white.
Another mix of the base coat was made using a couple of drops of Dark Earth and this was sprayed over the radome and various other panels. This was done to try and create a patchy finish as the aircraft I am modelling had a very worn paint scheme.
Once the decals are applied I will be using various grey panel line washes and then with a sponge or brush I will attempt to add the patches of light grey spray paint that you see on US Navy aircraft as a measure against corrosion control.
To be honest I'm very pleased with the finish as I've had major problems at this stage with a grainy or sandy texture in paint and I've put it down to either air pressure, paint drying out too fast as it leaves the airbrush, the distance from the model when spraying, over thinning paint, under thinning paint etc etc etc.
I had sort of solved it with the addition of acrylic retardent and flow improver liquid to paint mixes but after the ease of spraying this particular model I'm now wondering if there is a problem with Tamiya paint quality.