While most recipes call for a teaspoon or half a teaspoon of oil. We found we got a more even coating on some foods by decanting our choice of oil into a small spray bottle and using that. Never use one-calorie oil spray, which is a step too far in the diet stakes we found, producing nasty, chewy fries.
Most of the machines we tested couldn’t be used with fattier meats such as sausages or chicken or duck with the skin on. This sometimes results in meats being drier on the outside. This was where a spray oil came in handy and definitely improved results if not making them as good as if they’d been fried.