Ultimate Marvel vs Capcom 3 General

My one glaring problem as of now is the new team member switching can take a bit longer than I'd like to be, because if I press too fast my team member just appears and leaves. If I hold for too long I'm usually left open to at least one attack as I try to switch out. Am I doing it wrong, or working as intended?

Also, still trying to get used to all the vast possible moves one can do. I was an average/bad player in MvC2, so don't expect me to melt faces.

I had this problem at first too, but you eventually get used to the timing and don't really make that mistake after a bit.