First, welcome to Nitro Express!

I also answered on the other forum but will do so here as well.

There is no reason to think that a hammer gun would be more apt to double than a hammerless gun but this comes down to each individual rifle and how its triggers and tumblers or hammers have been tuned.
Try it with both hammers cocked on your gun and you will know soon enough if it is the best way to shoot your double. Of course, you don't have to have the second barrel loaded when you do this but it does add to the anticipation!

I have always cocked both hammers on my rifles as it just seems to make sense. I also shoot the front trigger first.

In the old days when hammer guns were the norm, I would bet that both hammers were cocked before approaching the intended game especially dangerous game.
Makes some sense that even when shooting harmless game that both hammers would be cocked as a misfire could be made up for with the minimum of movement and noise by simply moving to the other trigger.