Put a short (2"?) piece of Tygon clear vinyl aquarium size tubing on the end of the oil can delivery tube. Make sure the business end is cut clean and square. Push the tubing down squarely over the ball and pump. The oil will go past the ball and nowhere else. After a year or so the tubing starts getting hard, at least with the oil I use, so splurge and buy a couple feet of it for a lifetime supply! The tip of your oil can will also no longer scratch the paint and the shiny metal on your machines. The other little known problem with ball oilers is that if you push the ball too far into the hole it will stay there, and you will need to replace the oiler. Ask me how I know... 8^)
I suppose black rubber vacuum tubing would work, too, but I have not tried it yet. The clear tubing is nice because you can see the oil start to flow into the fitting.