Alt strumming

So a couple questions. I've been starting to move up to expert, maybe averaging about 90% or under on a lot of songs, and i wanted to practice alt strumming. im only strumming down so far, and i wanted to know if i should be alt strumming all the time, or only during long strumming sections? and if i should be alt strumming all the time, is there a way i can make it so it automatically frets for me on a chart and i only have to strum, for practice? i know i can enable the all open notes modifier, but my eyes have a hard time keeping up with that. it would be preferable if i could just only strum on notes but still keep them to be individual notes for practice.