Hi, Gav!  Yes, I make batches of washes ("Batches?  We ain't got no batches!"), because I've found it useful to keep enough of a wash beyond the completion of any given build, mostly black and brown shades.  I use craft store acrylics for these washes, and store them in little plastic jars that a friend of mine found in a thrift store and gave to me.

I use oils for washes, too, but those I make up on the fly.

I also grind my own pastel chalks and store the colors I use more frequently.  Colors I don't use as frequently, I grind on the fly.

Hope that helps!

Brad