I prefer blue marker for metal/metal. When I can't access a spot with a marker pen, I use a Bic lighter or one of those butane charcoal lighters; they work as well as a candle but I don't have to keep them lit.
For wood I use both Jerrow's black and pink lipstick.... when the black is gone I won't buy anymore. To me, more important than the medium is the applicator. I use a cheap artist's brush but I shorten the bristles by about half and use a pointillist technique....dabbing with the end of the bristles rather than brush strokes. Sort of like touching up a textured ceiling. It helps me get a nearly "dimensionless" layer of color.
