I have done faux woodgrains over steel doors and radiators and most times I have to correct the final color with a varnish that has pigments mixed into it. They can be tricky to work with because any area that is allowed to dry and then brushed over will be darker than the rest of it.
You may find it easier to use a Danish oil or Minwax "Antique oil". Both come in a light and dark finish. Without being able to look at what you have, it sounds like you have some areas where the origional finish has worn off and the wood is exposed. If the moisture from a damp rag makes the color the wood return to normal, then this may be the trick your looking for.