Either one or the other.

Ether is what is used.

Engines are harder to start and run hotter without enough ether. The engine will be over compressed I believe.

John Deere starter fluid was said to have the highest ether content of starter fluid. Put the starter fluid cans in the freezer. After chilling, invert can and depress nozzle to relieve pressure and use can opener to pop a hole in the bottom of the can. Pour contents into your container.

There are many types of ether. I don't know what type is used for model engines or where you can get it..