if it's digital, just make sure that the camera is in the same spot for all the pictures in the sequence, then go into photoshop and lay them all on top of eachother with the setting at 'transparent' or something. If it isn't digital, talk to a cool guy at your local photo store (an asshole would just tell you to fuck off). Also, make sure it's a big photo store, because a one-hour shithole won't be able to do it.