I have a pull-pull Browning Broadway that converts to release-pull by the insertion of one steel pivoting part with a wire spring. I don't know how close the Citori triggers are to the Broadway's but if you want photos of this part, send me a PM with your email address. Good luck.
Installing release triggers from scratch in a Browning Citori (and really, all other guns) is not a home gunsmith job. I have three of them with dbl release systems and it requires machine work beyond your grinder, file, and stone.
Send it to either:
Skeets Gun Shop, Tallequah, OK
Spears Gun Shop
Allems Gun Craft
Do yourself and all of us a favor by using one of these guys that do it for a living.