Having sailed on several barges in my youth and put the mainsail back into a barge on my own. I can tell you for certain that lower, middles and main brails are roved round the mainsail through cringles on the bolt rope, then back to the main mast, where you join the end of one side with a bowline knot on the other side of the luff side blocks. You then heave in the sail and pull on the double part of the brails together. Then proceed to the upper peak and lower peak brails and pull in one side then the other. They are separate ropes attaching on the bolt rope. the peaks having a eye spliced on the end and the rope goes through the cringle ( on the Mainsail leech )and back through the eye to the mast and then through blocks down to deck level. The lowers are also rigged through stirrup blocks attached to the mainsail so as to stop them fouling the bottom of the sail and deck fittings. A good book to have is an old publication, " A Handbook of Sailing Barges " by F.S Cooper and John Chancellr published by Adlard Coles of 8 Grafton Street, London. ISBN No 0 229 642322. Reissued in 1989 originally published 1955. F.S. Cooper was a well known sailing barge master in his time.