The Foundations are like super thick paints they work well as a first coat after the primer, they also work really well at covering something-up. I use to have to put at least 2 coats of the regular paints to cover the primer, but with the Foundations you only need one.
The Washes work like Inks accept they don't run if they get wet like the Inks could. Basically you use Inks to get into cracks and give quick shading like others have said before me.