You do not have to buy premixed glow fuel but you'll probably find it is a lot easier than blending your own.

The main point is that gasoline and two cycle oil intended to mix with gasoline are not compatible with your engine.

You need two or three ingredients to make glow fuel:
1. Methanol. Some race cars, go-karts, and motorcycles run on methanol so you can probably find a local source.
2. Oil that will mix with methanol. Castor oil is one choice. There are also synthetic oils or castor/synthetic blends that will work. The oil you use for your weed eater probably will not mix with methanol.
3. Nitromethane. This is optional but a huge majority of flyers in the US use fuel with it. Top Fuel dragsters use it. You may or may not find a local source.