I will state, as an amateur, that factory touch-up paint is the best for color matching and relatively inexpensive from Joe at
http://www.infinitipartsusa.com . The trick, as shown to me, is how to use it.
After shaking well, one should try to remove all the paint possible from the stem and brush by raking it against the inside edge of the bottle repeatedly until the brush is formed into a blade with very little paint on it. Then the paint is applied very sparingly by the tip of the brush blade thus formed. One does not fill the chip with paint, but rather fills it gradually layer by layer as described. Correct cleaning and preparation of the surface to be painted is required.
Painting over scratches and mars like Elwesso illustrated is more problematical. Gentle polishing should be attempted first. Using the techniques described above, I will use the Langka system and report back to the forum on the results. Being somewhat clumsy and impatient, if I can achieve decent results, anyone should be able to also.