Lathe oiler points

Hi guys. My lathe has several oiler points, these are like small round flush brass inserts with a small spring-loaded ball inside. They appear to have used a couple of different sizes for some obscure reason. I've never seemed to have much success using them, as although I have tried a couple of different oil cans (the ones with a thumb trigger) and conically shaped ends, after pressing the oil can tip into the insert and pushing the ball down, most of the oil seems just seems to 'squidge' out of the sides rather than go into the hole. Have I just got the wrong idea about HOW these need to be used? Thanks for any useful comments regards Mike