Starting to blog about the kind of work you do and showing examples will help you publicize the art you have made. Blogs can be obtained for free on the Internet, so you will not have to put up any cash, just engage your creativity. The blog can be a chance to discuss your passion, talking about the paints you use, the techniques you employ, and any other things that influence the art you make. If you use a blog site that shows your blog to other bloggers, this will increase your traffic and attract more interest in your work.
There are many airbrush magazines that will accept submissions. If a magazine likes your work, it may publish your pictures, which will give you maximum exposure to the people who are interested in airbrush artwork.
Many traditional galleries do not accept airbrush art, therefore, if you approach a gallery, you need to be very clever about how you pitch your work. It is often better to say you paint in acrylic. Then you may be given a chance to have your work considered properly. If you can't find a gallery that will show your work, ask at the local coffee house or restaurant if the owners would be willing to display your art. Often they are happy to do this, bu they may take a percentage if you sell any of the pieces there.