Bill wrote:

Can anybody advise me on the easiest method of pumping the oil out of
a lawnmower in order to change the oil?

Assuming you are referring to a smaller Briggs or Tecumsah engine built in the
past 10 years or so, just turn the mower on its side and let the oil drain out
of the fill tube. You don't need to get every last drop out and you don't need
to use the drain port on the bottom of the engine.