Some people think that using inks make the model look splotchy. One of my friends, (and also best painter in my group) decided not to use inks, but then quickly realized using inks recquire som skill too.
With that in mind, I will have to take back what I said about dipping in Devlan Mud. Inking and washing is a process just like painting. Pick a shade of osme colour, water it down if it is too thick, and apply to the areas of the shade intended only. And, as someone said in one of your other posts, your models are so clean and well painted, the inking process will be easy.
IMO, a careful application of Gryphonne Sepia on light skin (elves etc)m and use Devlan Mud (maybe a little watered down) on everything leather and cloth (also works great on chainmails!) in darker tones (brown etc). A thin coat of black works well on weapons (and this is, again, only how I would do it, and Im not an expert in anyway)
If you discover the models became splotchy, that should mean you just used too much ink/wash and should water it down even further.
But... you still CAN just dip the model in Devlan Mud, even if it is the cheap way (they even did this in a White Dwarf paint tutorial