Spool it on as tight as you can get it, overspool it slightly.
Go to a big field tie off your line off to a tree bench etc. Walk out til youre in your backing. Put a bend in the rod by pulling the line taught. Start reeling keeping your rod tip bent.
Or
If you've got a brave assistant have them hold the braid spool. While you crank the line on with the rod bent under load
its always fun when you speed up the braid spool gets hot and they drop it.
