I needed a shade of blue I didn't have so I decanted some Tamiya acrylic blue and black spray paint. I added black to the blue until I had the shade of midnight blue I wanted. The paint in the mixing cup was starting to skin over so I added some Tamiya acrylic thinner from a bottle. It didn't mix well but I airbrushed it anyway. It didn't go on as smooth as I wanted but it was OK for what I needed. I then poured out the little remaining paint I had in the airbrush, poured in some thinner swirled it around and sprayed the airbrush dry. The paint was still on the inside of the airbrush cup so I added some lacquer thinner, swirled it around and sprayed the airbrush dry and the paint was still on there. I got a Q-tip with lacquer thinner and scrubbed out the paint. It came out easily when rubbed. I then used commercial windex in the ultrasonic cleaner and cycled the airbrush through twice.

Is the Tamiya acrylic spray paint different enough from the bottled acrylics to cause these issues?

Is the Tamiya Spray can line acrylic? I thought all the Tamiya spray cans, TS, PS, and AS were some form of lacquer.

I think you might have gelled the paint when you added the alcohol based X-20A. You might need to soak your airbrush in cheap home depot lacquer thinner. I've also used acetone to clean dried paint before.

the Tamiya spray cans are not the a same as thier bottle acrylic(which are an acrylic lacquer). They would not play well with the normal Tamiya thinners as you discovered.
If you are going to decant and thin them you will need to use a lacquer thinner either Tamiyas, or I use a generic hardware store lacquer thinner as it's significantly cheaper..

The spray can paints can be thinned with Tamiya Lacquer thinner, but not the Alcohol based X20A as far as I know. I use Tamiya lacquer thinner to thin decanted paints, and it works really well.

Interestingly though, the acrylic paint from the jars can be thinned with either.

Because chemically, from what I've read, they are not a true acrylic.

The spray can paints are acrylic lacquer. The bottled paints are an aqueous acrylic. I believe that "acrylic" refers to an added polymer.

Thanks for your responses. Does that mean the Tamiya spray cans acrylic lacquer will adhere to the plastic better due to the lacquer thinner?

Probably, though it could craze some plastics. I've had no problem spraying directly on styrene, but "your mileage may vary". Its best to dust on the first 1 or 2 coats anyway, so that may be the saving grace.

I tend to use primer on all my models. The Tamiya lacquer spray primer on any material and under any paint. I've also used Velejo primer on styrene and under several different aqueous acrylic paints (including Tamiya) with no problems. I would not use the Velejo primer under lacquer of any kind.