I've had really poor results trying to brush Tamiya acrylics. Some people thin them with windshield wiper fluid, other people use various type of alcohol.

I've only airbrushed them and I use the Tamiya thinner for that. A lot of companies carry Tamiya acrylics. Here are some links to places that cater to plastic modeling:

http://www.greatmodels.com/
http://www.hobbylinc.com/
http://modelersvault.com/
http://www.phoenix-model.com/
http://www.squadron.com/

I don't know if all the above places carry Tamiya acrylics, but I'm sure at least a few of them do.

Here's the link to Tamiya as well:

http://www.tamiyausa.com/