AFter googling this same subject I found this thread. I wish there was a way to do this easily as well. One solution I found is to duplicate the comp you want to use the guides from, and then select all and delete the layers. Now you will have an empty comp with your guides in tack.
p.s. – This is a very old thread I don’t know if I am suppose to comment on old threads, but there still hasn’t been a solution so I figured I would put in my 2 sense.