You may also want to have an air hose just for spraying. Even though you remove the oiler, oil will still be inside the hose that was attached to the oiler and could still cause problems.

I have never used an in-line oiler. All my airtools (impact wrench, hammer chisel, air drill, etc.) have a place to add a few drops of air tool oil and I make it a practice to just do that before each use of the tool. Even if there is no specified port to oil the tool, you can just put a few drops down the connector before attaching the tool to the hose. If using the tool for an extended period, I add a few more drops from time to time. That has worked fine for me for many years and I have never had a failure of a tool.