Leaving finish in the bottom of a can will dry it out, but putting it into a soda bottle will keep it usable and is easy to squeeze out.
There are all sorts of ways to prevent varnish from skinning over or hardening in the can between uses. Here’s the tried-and-true technique I’ve been using for two decades: I pour my quart containers of finish into two clean, half-liter plastic soda bottles and cap them tightly. When the bottles are nearly full, it’s easy to squeeze the air out, but as the bottles empty I flatten them in a vise to expel the air. I’ve never had a bottle break, even when clamping down hard. It’s cheap and effective.
