I can definitely second Brian's comments about Vellejo. I have always been a worry wart and undercoated in Humbrol enamels on wargames models to get a good key coat in between the slightly soft pewter and the acrylic which may go on thin in places (My rubbish bottle shaking
) but it does have good pigment content.
I have only had a slight coverage problem with yellow (common with many yellows in many forms), but I learnt a tip from a figure painter for that so even that is cured.
With Vellejo, I have found the following:
1. The pigment settles and so, before use give it a blooming good shake. You will tell when the pigment is moving because the sound changes from a watery 'sloshy' sound, to a lumpier sound. Keep at it for a while longer.
2. Storing the bottles upside down is a good idea as well, to put the pigment near the nozzle, so even if you have shaken the bottle for Britain (or your nation
) and it hasn't completely mixed, you will bet paint and not carrier fluid.
3. The nozzle will bet clogged after a while and so, keep a needle or length of wire handy. I use the former or a piece of broken piercing saw blade handy for this job depending on which I have dropped into the maelstrom that is my bench.
3a. After a couple of years, the paint will start to go off, but the contents can still be used but you will have to remove cruddy paint from the whole nozzle piece. Remove the nozzle piece with a screwdriver and using an old pair of pointy tweezers, pull the piece of paint gunk out and dispose of. The lid will also benefit from periodic paint removal as this goes rubbery. Cleaning the lid and nozzle will reduce the latter complaint.
As a storage system, the Dropper bottle is good. I have never had a lid stuck on by old dry paint, I have never had the lid on my tinlet pop back up again because of excess paint build up, or the paint go dry prematurely.