Painting the joints is possible and provides a stiffer joint that will enable you to hold strong poses with your figurine. However if you stain the joints, any friction caused by movement will not erode the colour, even after any secondary paint you have applied has worn away.
You will need to allow your stained pieces to dry out, this will allow the pigment in the diluted paint or ink you added enough time to seep into the grain.
I recommend a timespan of 12 hours to allow all the parts to fully dry before assembling together. And there you have it, your new customised figure.
Painting the joints is possible and provides a stiffer joint that will enable you to hold strong poses with your figurine. However if you stain the joints, any friction caused by movement will not erode the colour, even after any secondary paint you have applied has worn away.