A while back Miles gave a good tip that I have used several times. Tighten the chuck on a hand drill to an old speedometer cable. The frayed end will chew it's way through almost anything. It has give and makes the corners. The sealer they use in the tanks will clog up the pickup tube if it is sealed without anything run into it before the sealant cures. I have also used the same trick on brake lines with good results. Just remember to trim the end of the cable by grinding not cutting with a saw or sheers.
Bill