As others have said, I use declarations for this. Our group limits declarations to once an action, so this really isn't a big deal (they could easily have used another declaration there). The only difference is that for really obvious things, I don't make them roll anything, though they still name the relevant skill that allows them to take advantage of it. And of course it has to make sense for what they are trying to do.
Example: someone turns the lights off. Mechanically, this is one of three things: a free action (that we'll call the player's declaration) to flip the switch, which is something really easy to do, or a supplemental action (so the lights were on a big lever, and I rule it as equal to trying to cross a zone, and we'll still call that a declaration, or a full action (the lever was REALLY big and hard to move, requiring a might roll) that we'll call a maneuver (because it's going to take someone else doing a maneuver to get the lights back on).
In the first instance, the player goes ahead and also ducks down to hide behind some machinery, with a stealth roll assisted by her declaration for the +2. In this last instance, the player also makes a declaration of "Hey this light switch is really hard to get to, behind some machinery, so as soon as I flip the switch I'm going to duck down for cover as well, okay?" Now she's got a +2 ready from the maneuver, and another +2 for hiding from her declaration, but she's going to wait until the next round to roll stealth.
The baddie decides to go silent as well, makes a declaration of "the lights just went out", and makes a maneuver (alertness roll opposed by player's stealth roll) of "I draw my gun and cock my ear to listen carefully"... netting him a +2 to whatever darkness can bring, as well as a +2 on a future alertness roll.
Player 2 tries to make for the door, with the intention of declaring the darkness towards his stealth roll as well. Instead I offer a fate point as I tag the darkness against him, and he accepts, tripping over some old machinery. The baddie uses his +2 on his alertness roll to hear this and target the player.
Player 2 goes ahead and hides, but we call it a her action, and she does so well (with her +4 from last time). despite the -1 for the supplemental action to go ahead and get her gun out. However, she goes ahead and declares (with her guns skill) that she's loaded with hollow-points, since she saw (before the lights went out) that the dude had no armor on. She'll tag it in a minute.
The baddie uses his darkness declaration from earlier, as well as his new declaration (Guns vs athletics: hey, i heard that guy go down, right? So he's off-balance for my attack) Which - while I simply said the player tripped, makes total sense, so the player is -if not on his butt - at least still stumbling or staggering. The baddie tags both of these for a +4 to his attack. Player 1 defends (taking some stress), and then tries to get away.. he'll once again use a declaration of darkness to aid in his stealth roll.
Player 2 now uses her guns skill (vs the baddies gun skill) to declare that she saw the guy's position in the muzzle flash from his round. She wins, taps both of her declarations to create a +4 bonus to her guns skill, tags one of her own aspects for a fate point, and is suddenly up +6 to hit the dude. She kindly reminds me that she's stealthed, so I roll an alertness roll for the baddie (who has already used his manuever's free tag, so he's SOL) and he gets caught unaware of the attack, with a defense at zero. If player 1 has even a +3 gun skill, she's now at +9 to his +0, and assuming they both roll flat, he's looking at 11 stress. That's enough to hit hard into his consequences, and he concedes (declaring with alertness that a window is nearby, and then fleeing out of it). Now player 2 turns the lights back on.
So. Basically, the scene condition was usable by everyone. But, it really gave them no more than they could have gotten by declaring other stuff. The benefit to them was that it required no roll. (Alternatively, you could have them roll with anything over a total of zero being successful, but I try to limit rolls.)
This can work even if the aspect isn't obvious. If the scene aspect is "scentless gas is filling the room", someone would have to discover that (scholarship once they start feeling woozy?) But that discovery, while it is an assessment that happens as a free action, works pretty much exactly like the declaration above. Once that person notifies everyone else, they can use it for their declarations, as well.
The reason I do this is that a smart player will quickly realize that there's no downside to trying declarations often... as often as they can think of them. So tagging the scene aspect as a declaration (rather than just for free) keeps them from tagging it for free, also making a declaration, and hitting +4 on rolls. So I find that it protects the fate point economy more than harms it.
That said, of course, the route to taking someone out tends to be a couple rounds of declaration+maneuver, then tagging those 4 aspects, with maybe one of your own fate points, to net +10 to your roll. But you have to be successful in all of those rolls, which are typically opposed. Because the scene aspects allow you to play off of them with no roll or low difficulty rolls (vs opposed rolls, which may be harder and have more of an element of chance as the opponent rolls as well), this system REALLY encourages them to be used, which means the scene aspect really flavors the scene. When those players go to describe that fight, the darkness there will REALLY matter in their recollection, because they relied on it so heavily mechanically. If it wasn't really taggable - if they couldn't mechanically interact with it - then it would be flavoring that might be mentioned in passing during a retelling.
So I also find that making scene aspects a little easy to interact with really lets them shine. It makes them a more important narrative tool.
Sorry for the long post, I just wanted to make a good case for why you should totally use scene aspects, all the time.
