bluewaterpig
Been building for a little while but I'm totally new to painting. What has me frustrated is mixing. From the research I've done, water seems to be the most practical thinning medium. Even though I seem to get the right consistency, I'm running into issues...
Bear in mind that "acrylic" does not mean "water-soluable". As an example of how confusing the terms can be, Pactra used to make a line of acrylic enamels.
Not all acrylics are water-soluable, though many prominent brands are.
Andrea's and Vallejo's acrylics are water-based, and can be thinned with water. Though Vallejo's airbrush colors are probably best thinned with the products in that particular product line.
Lifecolour's acrylics are also water-based and can be thinned with water.
The craft store acrylic paint brands Apple Barrel, Folk Art, and Americana are also all water-based, and can be thinned with water for applying by hand or with an airbrush.
By contrast, Tamiya's acrylics are not water-based, but alcohol-based. You'll read comments from some who use isopropyl to thin them, but I got poor results that way. I use Tamiya's proprietary thinner to thin their acrylics, both for airbrushing and for applying by hand. They can also be thinned with lacquer thinner, for airbrushing-it doesn't work so well when hand-brushing.
As to losing details on the piece, that makes me think you're applying too thick a coat. If you thin your acrylic paints properly, they'll be almost as opaque as a glaze, but you build up thin coats to achieve the colors, especially to apply shading and highlights.
For hand-brushing water-based paints, I recommend using a wet palette. A wet palette consists of an air-tight container, a sponge of some kind to hold water, and a piece of permeable paper to serve as the actual palette. You soak the sponge, put the paper over it and let the paper soak up the water, and then you can put drops of paint on the paper. The paint will thin on the palette paper, you can blend colors on it, it helps keep them thinned to a nice consistency, and you can close up the whole thing when you're session is done. The paints will stay "fresh" for a couple of days, and that's usually enough to cover several sessions. I'll add water to mine to keep it going. You can buy nice wet palettes, but you can make your own, too. My first one was a Chinese takeout container, a kitchen sponge, and brown packaging paper for the palette.
Hope that all helps!