I always put it together in paint and then piece things with PS.
You had the right thing going with your Island comic, bud. You're the one who is responsible for me wanting to do the fast motion effects in TZA, not MFZ comics, not Kaiser, not Jetz, you.
I just copy a row of the character's running sprites (depending on panel size, usually 2 or 3 poses) and paste it in photoshop, magic wand the background transparent then lower the opacity. Sometimes Wind + Motion Blur for extra speed.