Home Guy wrote:
Is it possible to only use part of a can of expanding foam for
something, then store the can and use it again later? Is there some
special trick to clearing the exit-hole after the first use so it can
be used a second time?

No, not usually.

They should make a half-can.

Liquid Nails comes in a "small project" tube for the times you don't need an
entire caulking cartridge.