Nick,
It's been a few seasons since I sailed sloop rigged but I still recall that it was simply a 3 or 5mm rope run through the sidestay shackle and attached to a pulley which was then fed through the jib sheet before it got to the trampoline or deck pulley. The rope was then run across the trampoline and an additional small cleat set up on the trampoline track (inboard side of each hull). Naturally this was done on both sides and the rope set up as a loop to avoid loose ends. If you run a 2:1 jib sheet then you need a double pulley.
I also recall having to set the barber hauler to maximum outboard setting then letting it off and sheeting the jib in the to get to the right setting. Setting the jib sheet first then trying to adjust the barber hauler was always much harder because of the force required against a jib sheet tension.
The trick was always to remember to let the tension off when approaching the bottom mark for the upwind legs.
Hope this helps.
Regards,
Peter Foulsum