For the very best results, the product should be applied in small over-lapping circles.
This ensures full surface coverage.
If you've applied typical paste or carnauba wax before, it's the exact same process.
This takes a little more time and effort, but if you want to save your arm, you can try applying back and forth too.
There is no right or wrong answer here :)
Just be sure to apply it thin, and to avoid plastic and rubber.