Can you use any kind of paint or do you need a specific paint for the machine

Most water or oil based paints, stains or finishes are fine. As long as it's thin enough for spraying. There are a few things you can do to paint/stain to ensure it sprays well. 1 - Stir the paint/stain with a mixer in a drill until its creamy smooth, about 1 min per gallon 2 - Strain the paint/stain before it goes into the sprayer 3 - Add a flow agent, like Floetrol or Paint Easy (this is not a thinner) for latex paint – Penetrol for oil based 4 - Or you can thin, even as little as 5% can make a big difference, water for water based materials and mineral spirit for oil based material.