Line and wash
You can either choose to paint first and then pick out features with pen as I have done or pick out features and then paint.
You can use ball point pens or permanent artist pens such as those made by one of the following; Faber-Castell, Unipen, Graphik, Stadler. Alternatively you could use Dip or Fountain pens using an ink that will withstand washes and will not bleed.
Starting with the line ...
.... and then add the wash
Starting with the wash and add the lines
If you need a refresher on line and wash, watch the Youtube video