Can you elaborate on the what you're talking about here? What do you mean by volunteers? You move them just for the nighttime? More questions, but if you can just explain your process maybe that'll clear it all up for me?
		
		
	 
 
In answer to the specific question...it is usually best to move the hen only at night to your preferred location as hens adapt better to the new area if introduced at night. This works best if you can move both nest box insert and hen at the same time as many hens attach to the EXACT nest they first set brood in. Some will refuse to move at all, pacing frantically until they return to the original location. This is not desired if their original location was causing problems. Once moved, the hen then is to remain in the preferred location for the duration of that brood and hatch.
 
As to what I am doing personally, since you asked for an overview....
 
I keep specific hens for broody purposes because, having burned down a coop with a heat lamp attempting to keep young pullets warm, I only hatch or foster with brooding hens (no lamps). Since I have proceeded down this path, I have found that the natural method is a superior method as I have experienced that it produces stronger and more vigorous chicks, more easily integrated into the environment and flock than the artificial heat lamp method.
 
To be able to regularly brood naturally, I have purposely sought out and purchased strong brooding hens, of the "annoyingly frequent brooding" types, and keep a "stable" of them 24/7 in a designated brooding hutch with attached run. That way when one enters into one of their frequent broods, I am prepared and already set up. 
 
I currently have 1 bantam Silkie, a proven brooding queen, and 2 bantam Cochins  who are young pullets "in training" (of a breed and from a particular line known for excellent brooding). Having these brooding queens in a designated brooding hutch/run keeps them safe from the constant hazing I experienced with my bantams from the large fowl flock (as they are inevitably on the lowest pecking order being smaller bantams). As stated, it also allows me to be in instant preparation for when one of these ladies sets into a good brood as they will do so within one of the 2 nests I have in that brooding hutch, ie they are already where they should be, isolated and safe, with ideal nests, for proper setting of eggs. That way I do not risk having a hen refuse to move (and abandon eggs), and I have them well settled by the time any expensive eggs arrive.
 
I have grown into this set up over the years for numerous reasons...I have had very poor results with communal brooding, which for me resulted in lost of valuable eggs (I purchase specialty breeds to hatch at $). In the communal nest, it was always the fertile eggs that got kicked out and stomped and broken. Or these eggs were the ones on the fringe of the hen and getting cold as she attempted to sit on an ever growing mountain of clutch.
 
I also have hawk predators that love a quick snack on little chicken nuggets (aka young chicks and pullets), so I cannot afford to have my valuable chicks being picked off in free range, nor my most valuable broody bantams (I lost my absolute favorite brooding queen this last fall when I succumbed to a gorgeous day and let her out with overgrown youngsters...the Coooper's Hawk picked her off that afternoon.). For those of us who make a regular habit of brooding, you soon realize just how valuable a true brooding queen and mother is...they do not come easily and you feel their loss keenly as you can almost plan your hatching program with some certainty with them in mind.
 
As to what I mean by "volunteer"....
If I have a "volunteer" from the main flock, that means a large fowl bird not known for being broody has suddenly surprised me with a volunteer brood. (I have actually had good success with several of these gals once I established they are serious). They, due to their location, set up shop in the main coops, taking up 1 of the 4 nests I have open to them..which usually clogs up traffic since they inevitably choose the "golden nest box"....the one and only box any of them will lay in that week (it changes from time to time for no apparent reason). As I keep an average of 14 laying hens at any given time, that is a lot of traffic going through.This caused quite the pile up in the nest box and the mishaps with the eggs mentioned above, Further I saw lesser dominant hens pushed out of the nest as they wearied of the dog pile. I also witnessed that the dog pile follows them...it is chicken nature...if a hen is sitting there, it MUST be a good place to lay. So the less assertive hen gets pushed around from nest to nest with valuable eggs left in the wake and the hen fretful and unsettled.
 
I also have eggs that I sell and can't afford to let them get kicked around in the dog pile either. Plus the additional squawking and shuffling of unhappy hens. In general, one hormonal and broody hen, clogging up the nest boxes produced havoc all around.
 
I ended all that by building a designated brooding hutch. Now I no longer attempt to do any brooding in the main coop. After determining a "volunteer" is truly serious, by her setting up shop for a couple of days. I move her at night into one of the open brooding hutch nests. Once (and if) she settles there, I then place fertile eggs under her for hatching in the brooding hutch. I have removable partitions which I can place within the hutch to subdivide off hens from each other so that they are not disturbed if I have an LF hen among my banties. I haven't had any real volunteers of late (the last year), so I am likely only going to use my faithful banties, which is perfectly fine with me as I prefer my big girls laying nice eggs for my family and for my customers.
 
But that's what works for me with my conditions and goals. Communal brooding is possible with the right flock chemistry and set up, especially with smaller flocks...although @fisherlady  has had great success with communal brooding in a larger flock situation...but she has set up designated areas of retreat and has worked hard to build the right kind of chemistry in her flock to be able to do that. Some are able to do it right off because they were lucky that the flock was right and it worked. Others have had disasters brought on by typical chicken behavior.
 
Each flock owner must assess their flock and conditions and do what is best for them.
 
Good luck on your broody project. Keep us posted.
 
LofMc