In Tutorial Hills, I find that I cant actually fly and I have to support myself with the water jetpack thing. I end up falling back onto gusts of air which lift me back up, but it seems that there aren't any for the 2nd feather, so I'm struggling to complete the star challenge with the super feather

do a triple jump or a dive to start flying! from there, you simply have to be careful with your momentum. it's sort of like flying a glider :)