I have been using this with Vallejo primer. By adding a few drops it extends the drying tome and eases the flow from my airbrush.

Purchased this to use on my model railroad locomotives and rolling stock. The thinner works well with the airbrush colors that don't come pre-mixed to brush with. Just add a little to your reservoir and it comes out nice and smooth.

If you're using Vallejo water works but this is the right tool for the job and works much better. If you're using Vallejo paints you need this.