A: Use a non-reactive, non-drying airbrush lube.
The trouble with lubricants is the fact that they generally don’t get along very well with various kinds of paint. Think of mixing oil and water and spraying it in tiny droplets all over your work. If you’re making a custard or some other kind of food item (like salad dressing) that mixes oil and water with an emulsifier this would be wonderful…but we’re not decorating cakes or spraying dressing onto a salad (at least, most of you aren’t decorating cakes…)
Paint doesn’t like lube. There’s a lot of things paint doesn’t like, but airbrush lube, if used in large enough quantities, can still cause you grief. But the grief is easily avoided. Simply put a tiny half drop of lube into the right spots and viola. You’ve got an airbrush that feels like new.
Glycerin, available in many drug stores, it does dry out so you will have to apply this lube more often than the other kinds.
Super Lube, as a general rule of thumb, rocks your socks. It’s non-reactive with most paints.
Though I’ve never actually used it, I’ve been told many good things about it from people I’d trust to make that kind of recommendation.
Cooking oil works for chefs and decorators, for painters cooking oil is a terribly bad idea.
You’re not normally worried about mixing the oil with the food, just make sure you use the kind of oil you wouldn’t mind tasting just a bit if you get a little over zealous in your application.