Hi Toshi,
You have downsized to a 1/48 scale eh? I do a lot of brush painting because I like to do it more then I like cleaning an airbrush. Think of it like a 3D painting and then use the same techniques an artist will use for softening and blending the colors. Most important is to make sure the paint is not to thick, or not too thin, and to use a good, flat brush that will stay loaded up with paint, and use light strokes to thin out and prevent those dreaded stroke marks.
You may want to soften your lines between the dark and light colors by mixing the lighter color with a tad of the darker to make a balance tone and using a very soft, broad, flat brush, dry brush along the edge and soften it up so it blends. It takes some practice but it is a fun excersize. Again, like doing a 3d painting.
Now, like if you airbrushed it, give it some washes of light gray on the light colors and black/brown over the dark colors, again to soften up the tone. Weather if you want. Then follow up with your final clear coat. You did a cool job on the 109, and those same techniques would look great on this project as well. I wish I could include pictures but my Photobucket account has gone kaput and I'm still working at getting it fixed. Scott