I used one of the syphons with the brass primer on the end that you shake to get flowing. I got my tank about 99% empty and then used a shotgun cleaning mop to swab out almost all of the junk in the tank.
I know you already know this but I'll say it for any guests reading: DO NOT use any kind of electric syphon or vacuum to empty the tank unless you really want to remove all of the hair on your head....or worse!