I start out with it empty,
but as I use my brushes,
I place them in the slots,
and if possible in the order of the colour wheel.That way I can get more out of an already used brush if the colour on it works again on its own, or as part of a mix. Once the holes are all full with used up brushes, I usually clean them all and start fresh again.
As for cleaning brushes quickly before almost immediate reuse, a friend of mine recommended a a gentle and deep rubbing through with a tossable cotton cloth and a quick rinse with dishwashing liquid and water ...this can save relying on turpentine every time!
I also like to keep dry brushes and Q-tips handy simply for scraping through a wet layer of paint to the reveal the dry layer of differing shade underneath, or even to wipe off excess from heavy-handed dabs, rather than smudge them with a cloth.
Speaking of Smudge, here she is keeping me company on her favourite sleeping chair in the studio.
I love having my pets around while I paint. Usually Seeker will plop down on the rug and watch me with one eye while watching the cat with the other, or give me advice on shading and such:
And of course, for the dreamer who lives inside of books far too much, pets are willing to oblige without questions as well...blurring out now....envisioning...dancers of some sort, in fluffy aqua tutus against mild russet walls....and caramel orange smudges.....