Marvel Mystery Oil. Specifically, the original stuff. By brand name. Contrary to my typical advice, "Air Tool Oil" is maybe not the best solution for an air tool. Maybe in a lab somewhere. (Maybe......). But in the real world, Marvel Mystery oil.
If you use an air tool a couple of times a week or more, a couple or three drops each morning before the first use, and you're good for all day. That's not much. It's pretty thin stuff, it makes smallish drops, but its all you need.
If you use your air tool infrequently, shift the recommended oiling to the end of the day. Oil it before you put it away. Same few drops, and run the motor for a few seconds. Forward or reverse doesn't matter, the air just goes different ways in the same places. Just put it in there and give it a quick buzz.
It doesn't take much, it just takes diligence. I won't say that there is "nobody" making a quality air tool oil, but I havn't seen it yet. 30 plus running air tools daily, on "not horrible but still questionable" air, ranging from used a lot most days to used yearly or less. I've worn out plenty of air tools, but not in the air-oiled parts since I stopped using air tool oil.
The only exceptinon I have to that is reciprocating pistons. Air hammers/air chisels, needle scalers, and the like. Oil them VERY seldomly, and very sparingly. Same Mystery oil, just not often. They work different.