As an Old, Hand Lettering Sign Painter I can tell you there are any number of Good Brand name "paints" that can be used on our models that come in 1/2pt to Gallon sizes.
Your not very likely to find them at our local hobby shop though. You'll need to visit, paint, Craft and most important Sign supply shops, either brick and mortor or on-line. Dick Blick on-line might be a convenient place to start.
Hand painting like most skills takes some practice. There are a bunch of techniques that can aid in making our hand painted results almost indistinguishable from Sprayed applications, but rather then type another thread may I invite you to visit narhams.org website library under Tech-Tips If memory serves Tech-tip-005 covers Brushes and hand painting details which also contains some very important paint application techniques that will help hand painting entire models
One of your main concerns will be getting whatever type paint you decide to use to the proper consistancy to flow correctly without running. this is a "feel" thing and has to be practiced but is easly picked up as you go. I'd suggest practicing on scrap tubes and balsa stock to understand what I mean by proper flow. This can be done with very inexpensive tempra or watercolors as well once the tube has been primer sealed. I wouldn't suggest these for the finished models as they don't adhear to well to flexing tubes
but they can and have been used on Mod-rocs in the past.
If your new to painting i'd suggest trying acrylics was they thin with water and/or mediums that don't produce much of an odor.
If your not to worried about the smell, I strongly suggest 1-shot lettering enamels, Bulletin, or Acrylic coatings for superior durability and color selection. Ronan is another "Bulletin Enamel" manufacturerer worth looking at.
Hope this helps a little.