more simple than that,a long exposure time like 30 seconds. this way,the person can change it's possition & all of the possitions will be recorded in the same photo.
the tricky part is for that person to change positions very fast & keep a decent time standing still for every position : example - for 30 seconds shutter & 3 moves required,that person must stay still for about 8 seconds per position.
it's also much easier if you can control the light source,like a flash,to use it only when the person rests in a certain position. this way,no movement trail will be visibile.
Sounds like it would be a disaster that way!!
Im guessing in photoshop you would layer the diffrent pictures?