Tamiya acrylics can go down grainy in the right conditions (dry atmosphere, high pressure, big distance) & this retarder helps prevent this, it can also help with airbrush dry tip issues.
You mix it in with the paint or you can mix it with the thinner before thinning the paint. It can be used up to a 1:10 ratio with Tamiya Acrylic Paints.
You must remember that like most other retarders, adding too much retarder causes the paint to not dry.
Also, it is ideal for painting glossy finish surfaces and what I found very useful is using it when brushing Tamiya acrylics. As when brushing the paint starts to cure between brush strokes and using a good mix of paint, Tamiya X-20A thinner and Tamiya's Paint this can help prevent the quick drying that normally occurs.
This is a fantastic product to add with the use of Tamiya paints and I have found it a great addition to my tool box!
Thanks go to Tamiya for providing this set to review and IPMS USA for allowing me to review it for them.