Camouflage is an optional skill. Rather than deploying a unit in camo state, could I deploy Briscard Jacques normally out of camo state, run him around on turn 1 and shoot some things, then activate his camo state at the end of the turn using my 1 use of it to protect him going into turn 2?
You mean going camo for free at the end of your turn? No, you cant. You can optionally resing from deploying in camo, but it is not there anymore, hanging out for you to use at any point of the game.
You can't enter camo for free the same way as holoechoes, but there's no rule that says models with camouflage (whether single use or normal) must be deployed as markers. So Bruant can be deployed as a normal model and then spend an order to enter the camo state later in the game, but only once.
