What is your opinion of Vallejo Inks in relation to Citidel Inks? I'm looking for a better wash.

I've used them both and really haven't had a problem with either other than the citadel ones will dry out overnight if the cap isn't on tight. And I mean that literally they will completely dry out in one night.

Give the ink a good shaking to make sure the pigment is mixed in well.

I like to use 2 liter pop bottle caps for mixing my inks. Add a little water to the cap. Then add a few drops of ink until I get the coverage I want.
Vallejo offers more control in this department as you can easily squeeze in a drop or two of ink vs drops from a brush with citadel. But on the other side it's easy to use ink straight from the pot citadel if you want full strength ink, and only a small amount. (like for out lining).