I have fine hair.. don’t know about ‘extremely’. It took me years of trial and error to figure out what worked, but since I have, my hair and I have a pretty good relationship. The key, for me, is conditioner. Without it, my hair looks and acts rather frightful and can be very difficult to manage. With it, I rarely need a brush (finger combing works fine).
I don’t know about your hair, but my hair has a tendency to get kind of frizzy and prone to fly-aways. Eventually, I realized that volumizing stuff wasn’t helping much, but that might work for you. Pantene has a line of ‘silk and smooth’ products that make the hair soft and weigh it down a bit (which I definitely need), but not too much.
I am currently very fond of Tresemme products. I use the Thermal Recovery line most often because I blow dry and occasionally straight-iron my hair. I also have a Tresemme deep conditioner to moisturize my hair once or twice a week, to hopefully mitigate the effects of the coloring I’ve been doing.
Anyway, you should check out the Tresemme site. There’s a product picker in there somewhere, where it walks you through and picks the right products for your type of hair. I don’t get paid for pushing Tresemme, by the way, but I do love it and have been using it for years. It’s very affordable and works great with my hair—I have no need for more expensive salon products.