When I let my hair air dry it becomes somewhat frizzy. What can I use after a shower to reduce the friz?

I have very long hair (down to my ) and I've never used hair products on a regular basis. For a while now I've just been pulling it back when it's wet because the friz is bothersome. I would describe my hair as soft, pretty straight (maybe a slight wave), a bit thin, and not oily. When I use a hair dryer my hair is much more managable, but it take about 30 minutes to blow dry!! Any suggestions on specific products that might reduce the friz and leave the hair looking untreated? I just want to leave my hair down to dry for once. Thanks :)