Other tips :
Use a comb to detangle your hair, for the fine tangles i use a small comb with very small spaces in between (the kind used for leech). A brush is great but it's also a volume killer
. i only use it when i know i'm going to wash my hair, and on my lengths while gently holding them in my other hand.
When my hair is wet i use a detangling comb.
I cannot suggest a volumising mousse, all of those i tried created build up and greased my roots.
Instead what you can do is use a hairspray (good old Elnett for me), and apply some at your roots with your hair down, and run your fingers through your hair to distribute it. Only use a little, and it will give an extra volume to your hair. I usually finish by setting everything with a final spray of elnett.
Avoid heat tools, use moderately your conditioner. I only wash my hair when the roots are greasy, every 2 to 3 days, huge progress as i used to wash my hair everyday.
Also avoid twisting your hair, it causes breakage and fine hair is more fragile. I love braiding my hair for work, but now i just use a big clip and it seems to help my lengths.
Finally, getting trims regularly is important, to keep your hair in shape.