THE ANSWER!
Well, some of you got it, some of you didn't, and some of you got it wrong!
As many of you know, the old Vaqueros released the cylinder for loading simply by opening the loading gate. Unfortunately, this did not allow reverse indexing by feel to line up the charge holes for loading and unloading. It had to be done visually, and if you missed one, you had to go around again to get to that chamber.
These guns have been altered by conversion kits from Ron Power (Power Custom). Now they operate exactly like the older Blackhawks and Colt Single Action Armies. You place the hammer on half cock, open the loading gate, and load or unload by feel, reverse-indexing the cylinder to line things up for loading or unloading. You can do it in the dark, and it's much faster. Normal Vaqueros do not have a half-cock notch on the hammer, but these do. This gives a "3 click" sound when the hammer is cocked fully - not quite as nice as the old "4 click" sound of the old Colts (no safety notch on the conversion hammer), but far more satisfactory than the "2 click" sound of the normal Vaquero.
Also, it should be understood that
these guns can be loaded safely with 6 rounds. The transfer-bar action is retained, making the gun safe with the hammer down on a loaded round. So you have the best of both worlds - the safety of the modern Vaquero with the feel and convenience of the older action that allows fast loading and unloading with the hammer on half cock!
Those of you with Vaqueros should find these conversion kits very satisfactory - I know I do.
John