When you load the brush, if you find its too wet, touch the hairs where they meet the ferrule with the edge of a tissue or paper towel. This will draw out some of the excess water and make it easier to apply the pigment. As you become comfortable with acrylics, you'll also find that what may look indiscernible when first applied, will darken or lighten depending on whether you're shading or highlighting. i.e. Even though you mixed in some darker color, when first applied it may not look like you did anything, but as it dries, you'll see it darken where applied.
With the vallejos, I've also found that as you layer the colors, adding a second coat of the same ratio will enhance the color. i.e. 1 layer at 4:1 leaves a tint, the second layer at 4:1 is a little more opaque and adds more pigment. This way you can transition between successive layers easier.
Adding a glaze over your highlights and shadows will also smooth out some of the transitional layers.

What ratio do you suggest for a "glaze"?

Terry, I like to be a little more conservative with my glazes, I'll usually mix up a 4:1-5:1 wash. Easier to go over it a few times than to try and remove. As Carl suggest, a "tinted water" is best. Some colors contain more pigment in them so you'll have to adjust accordingly.

For better work I suggested you to use distilled water, and I like to use a drop of glaze meduim for having better result than only water. And the finish is always matt at the end of my work.