with the 3x xp you can get to level 22 in under 10 hours, so unless you are really attached to those characters you should just cancel the subs on your existing accounts and start new ones.

There are two basic scenarios - in number one, you have a level 70 booster, and in number two, all your characters are the same level.

If you have a booster, DO NOT RAF FROM THAT ACCOUNT. A level 70 who has referred someone else in the party will invalidate the 3x xp from boosting for everyone in the party, but as long as the 70 is not a referrer for anyone its fine. So with a 70, you setup 4 new accounts and chain RAFs from them - ie new1 refers new2 who refers new3 who refers new4 (new1 <-> new2 are linked, new2 <-> new3, are linked, new3 <-> new4 are linked). DO NOT send out a refer a friend from your 70 account. You can make a party of 70 + new1-4 and instance boost away to 60 with full 3x bonus.

If you do not have a booster, then you can take any of your existing accounts, make it the referral starter, and chain them up (veteran->new1->new2->etc). All 5 can group up and as long as they are all the same level you will get 3x xp per account and quest/instance your way to 60.