Didnt quiet get that, but the way i remake the replays.. uhh.. is by moving a part off the body, on the frame i want something to happen, because in that way, all the information gets written to the script, and then you simply tell it what to do.

For example, if i would want uke to be a exploding firework -like you intended, i would move a joint on uke on the frame i wanted him to blow up on, and then go edid the script, on the frame that then has come. In this case, i would add some velocity up and to the sides, and crushing some parts. perhaps also adding some spin.

Hope that helps.