Print spotting techniques vary. Fade-proof India ink used to be used (maybe still is) by many leading photographers, using an extremely fine stippling technique to darken areas larger than a small point. Done well, at normal viewing distance one only sees it with close examination.

The venerable Spotone dye has not been made for many years. Marshall's still makes some, but the two don't blend in solution; you use one or the other.
For newcomers using Marshall's (like me), I offer at least a starting point for attempting to match color/tone with the paper I use mainly, for areas in which a lighter-than-black spotting is needed. This can only be very general; variables abound, especially with the addition of toning. If anyone has more precise recipes, please post!

For untoned WTF, try
5 drops of Neutral Black
4 drops of Blue Black
3 drops of Selenium Brown
½ to 1 drop of Brown (strong stuff!)

Because with the VC papers selenium toner affects the darker values more than the lighter, fairly full toning may indicate two recipes for spotting dye.
For rich brown tones resulting from toning in about 1:5 selenium toner for several minutes, for the darker values try
3 drops of Neutral Black
1 drop of Blue Black
1 Drop of Brown

For the middle and higher values, and for more dilute toning solutions (such as 1:19) where toning is not carried so far, the following may get you in the ballpark:
4 drops of Neutral Black
1 drop of Blue Black
1 drop of Brown