Re: Gaff rig main dousing
Your answer is lazy jacks - they do the same job on a gaff rigged main as they do on a bermudan main. You can rig 'em exactly the same way too, so they can be tucked down out of the way when not needed, and pulled up otherwise.
Avoid attaching them to your topping lifts, if you have them (and you should, they provide invaluable control of the sail shape, and help reduce sail stretch), and be sure to keep them clear of the topsail running gear too, if you have it (and you should - big-ass jackyarded topsails are one of the best bits about a gaff rig!).