what is the best way to go about showing my character have a flashback using only FCP 5.1.2?

i have footage of my character staring at himself in the mirror and another sequence/scene that i want him to flash back to. can this be done in FCP only without looking cheap?

fade to white and back a couple of times...or white flickers.or just have the image fade in over the "now" stuff...to superimpose interesting combinations of images (see "Apocalypse Now", right at the beginning). Any way you can think to do it...frame then and now shots to have visual similarities entering and exiting them (see "Highlander", The original one, the rest don't count ;) ).