I find that neither Model Master Acryl of Tamiya acrylics do the job well when it comes to hand-painting. They do provide nice results, but not without several applications. Generally, you'll want to lay down the first coat, smoothly, and in one direction, without running the brush back and forth. Make sure this initial layer is dried well. I've found in the past with Tamiya paints that if the first layer isn't reasonably dry, the second, if brushed back and forth, will remove the first. Definitely a pain, but it's the nature of the beast. Even with enamels, I think you'll be hard pressed to create a flawless, opaque result on the first layer.
The BEST acrylics i've found for hand painting are the Citadel colour range. They're paints that cater to the Warhammer war-gaming crowd. Water based, non-toxic, and possibly the best results when it comes to hand-painting. Keep in mind however, the paint is not as thin as other hobby paints, so more care is needed not to overdo it, and most colours such as olive drab, will have to be mixed. They do have a wide range however, so I'm sure you'll find a good basis to work from, if you chose to try them.