Hi Gower,
Yes you can spray water-based finishes, just thin with water to the desired viscosity. A viscosity cup is very useful to get the correct amount of dilution. The cup has a hole in the bottom and you fill it with your paint and time how long it takes to run through. Paint spraying uses quite a lot of air and small compressors will struggle to keep up. You also get a lot of overspray, lots of your paint in the air and only 20% ever getting onto your workpiece. Most, if not all the compressors I've seen have some sort of pressure regulator because different tools have different pressure requirements. I got reasonable results using my cheapo 24 litre compressor and the gravity fed spray gun that came bundled with it. From memory I think 35 psi was a reasonable pressure to start at...you have to play around with the settings to get it working well...that setting still gave a fair bit of overspray but much less and it wouldn't atomise the paint properly. I have now moved over th a HVLP system (B&Q Performance Power, not sold anymore) that has its own turbine that blows a high volume of air at much lower pressure (HVLP). This set-up gives pretty good results with water-based paints and much less overspray. Be careful if you intend to try solvent based paints as you can generate a potentially explosive atmosphere.
