There are so many ways you could do it. You could roto a matte for the sabre, you could use the keyer to pull a matte, you could use a travelling selection, you could hand paint each frame etc. etc. If you want to get an intro to combustion there is a simple and quick tutorial here http://www.digitalvideoediting.com/2004/03_mar/tutorials/ceyeaeguy1.htm and buckets of others on the web