I do a lot of painting and providing clean, dry air is a pain. I have a commercial level compressor and run a water trap, a 5 micron particulate filter, and a coalescing filter.

The water trap takes out about 50 percent of the moisture, the particulate filter is good for dust particles, the coalescing filter takes out the rest of the water and any oil from the compressor.

For the price of those filters alone, you could get a nitrogen or CO2 tank, and a dual guage setup. The "air" will be cleaner and dryer than what you'll get out of a compressor setup. The dual guage setup will allow you read the pressure in the tank (guage 1) and set the outflow pressure (guage 2). If you want do it differently, get a guage and a flow meter.

With a flow meter, you can set a very low constant flow rate (like 5 or 10 cubic feet per hour). With a dual guage setup, you would set the out going gas pressure in pounds per square inch or Pascals (if you're metrically inclined).

If you go the guage route, make sure the guages are compatible with the type of gas you're using. The orfice sizes are different inside the guages to account for the different gas types. In other words, you don't want to use an acetylene guage with nitrogen.

Flow meters are a different deal. They don't really care about the gas type, the just flow the amount of gas you set.