It depends on if you need some decent pressure. Some lube locations can work with a drip feed oiler. My lathe and mill fittings all seem to need a bit of pressure. I fiddled around with a few squirt oilers, that worked for about 80% of the fittings. I can't imagine trying to fit in one shot oilers - that would be crazy effort. There are various efforts described on line to convert a regular grease gun, or a push grease gun (for power saw roller nose bar).
I finally broke down and purchased a Reilang oil gun. It has a changeable end so you can use it on the cup or nipple style fittings, it doesn't leak, works at any angle, delivers decent pressure. I wish I'd bought it years earlier. Yes, it was expensive, but a lot cheaper than not getting oil where it needs to be. Cheaping out on the lube efforts is a false economy.