Grease them, oil them, glass smooth floor, they still suck if the car is heavy, especially if it sits on them for 6 months. The wheels are cheap junk, which is what I paid for. They work well for moving an empty shell of a car. There are 2 versions of wheels, some are flat, some are a little rounded...flat roll even harder.
I admit my car is a basic shell, has a 440/AT/Dana in it but no fenders, glass, or interior. I haven't noticed if the wheels on mine are flat or rounded, they're years old though.
I haven't greased the wheels, just make sure they're pointing the right direction, find a good solid place to push, and kind of rock it (push,push,push) until it starts moving. This is just to move the inop car around in a 2 bay garage. Maybe the expensive easy rollers would be worth it if I was pushing the car from one end of a huge shop to another, but I'm not.
