Kaminoan

Hello All, I am new to these forums. I am a Lego customizer and have been expanding my skills and trying to learn some new ones. I was directed here because of the talent and experience of the members. So I am going to jump into my current customizing issues. I recently purchased an airbrush off of e-bay, used of course. It is a Model Masters Professional brush that has single action, double action, and fixed double action, but I don't really know what this means. The instructions tell me how to set the brush to each of these settings, but they don't tell me the difference between them. Can anyone explain? Also I have a lot of model paint from my old days of plastic airplane models. Can I use this type of paint, it is all Testors paint? Do I need to dilute this paint? How do I do that? I understand I am asking a ton of questions, if anyone can direct me to a resource where I can find most of the answers, I will happily dig them up. I just wasn't able to find much with my initial searches, can you help me? Thanks Jared