I only have one halyard attached to the gaff and this does not need to be disconnected. To harbour furl I go into wind and furl the jib, bringing the mizzen in hard to keep the boat head to wind. If it is blowing hard I might lift the rudder to stop a reverse turn. Then I disconnect the main sheet. Then release the outhaul and lift the boom out from the gooseneck (leaving the boom attached to the sail). I then lift the boom so it is parallel to the leech and tightly wind the sail round the boom until the sail, now wrapped round the boom, is parallel to the mast, with the gaff still in position. Then I take the spinnaker halyard and wrap it round the furled sail, as high as I can manage, to prevent the wind from catching in the top of the sail and causing it to flap, securing the spinnaker halyard on its cleat.
On the BR17 I have never had a problem doing this, even in gusty conditions, and the furled sail is secure for a return to shore and for temporary mooring.
You need a couple of practice runs, nut once mastered it is a very easy and tidy way to furl the sail, without having the boom and sail getting in the way. There is of course less room in a BR17 than a BR20.