This stage of building your model can often be the most time-consuming, and it is worth taking your time here. Painting is often the "make or break" step in building a model. An otherwise poor kit can still look like a winner with a snappy paint & finish job. Conversely, a wonderful kit can be ruined by a shoddy job. My paint jobs go through several steps. Yeah, like you're surprised.
I usually prime the model with a coat of neutral flat gray. Applying a primer coat of serves a number of purposes. This is the last chance to find imperfections in the model before the real paint goes on. Right now your model may be a mix of colors - the color(s) of the parts, the green of putty, and so on - and it may have dull and shiny areas. The uniform color of the primer lets you carefully check the surface for areas you may have missed while puttying & sanding. You can step back and re-finish these areas. Primer also gives you a uniform "canvas" for your main colors.
What's not to prime? If an area is going to have a rubbed metallic finish (such as Metallizer or SNJ Metallics), I'll either gloss-prime it, or not prime it at all.
There will typically be one color which covers most of the model's surface. I'll usually lay down this color first. There are times, however, when I'll paint patches of a detail color and then mask those off before the main color goes on. Most often, this will be because masking can be applied easier to the detail areas. As time goes on, you'll figure out for yourself when to go that route.
For all but the simplest paintjobs, you'll eventually need to mask off part of the model before applying additional colors. The main watchword here is to make darn sure your masking will do its job: to keep the next color of paint off the previously-painted area.
What makes a color a detail color? Good question. For some paint jobs, you'll find yourself going through and insane number of iterations of the mask - paint cycle. What can I say? You gotta do what you gotta do.
And finally, there are those little bits of color here and there - the glossy black tip of a control stick, the various colors for instrumentation, silvery bits on landing gear, and of course all the detail that goes into painting figures. They'll drive you mad if you let them.
The Model Citizen's "Sprue U" pages are �2004 Roger Sorensen
last updated 04 December, 2007