"raymondj"
That's great except that I frequently have to varnish something that
requires the brush to be turned upside down (think about varnishing
something on a ceiling.)

The painter we had last time varnished a ceiling, using a tiny roller that
fit into the gallon can, and rolling it on a smallish area with that, then
brushing it out with a good brush.. This meant the brush took a long time to
saturate to the ferrule. The roller was a throw away type.
And sorry about that earlier advice re using a final detergent rinse to wash
out the brush - do that with synthetic bristles only when using oil paints,
not natural bristles.