A process and machine for refilling and reusing or recycling spent “bag on valve”-type aerosol cans. The process includes drawing a premeasured amount of liquid product into a refilling module, followed by pushing the product into the product bag (that surrounds the bag on valve), acting against the pressure of the gas already in the can. Opposite-acting, one-way valves in the inlet and outlet of the refilling module enable the drawing and pushing action. One size or type of refilling module is easy to swap with another.