A chainwhip is a very simple tool, easily made with a few bits of chain ( doesn't even have to be new), and a piece of metal bar of the correct thickness. Old freewheels can be very difficult to take apart, even with chainwhips. The cogs can be unbelievably tight. Unless you have access to good condition replacement cogs of the correct type, removing freewheel cogs is pretty unrewarding. When I could no longer obtain replacement cogs for my Sachs 7 speed freewheels, I stopped trying to remove them. Too bad, these freewheels had a grease port that was exposed when the cogs had been removed, you could easily lube them and keep them running like new