I've found through trial and error (generally a lot of error) that it is most often a waste to buy a large size bottle of the stuff. Despite various methods to try and keep the stuff from clogging or generally building up to the point where the bottle becomes useless, it invariably seems to happen. I've tried using wood nails/push pins in the top to seal the bottle (inert metal vs. directly stuck cap), wiping off the bottle and slapping the lid on tight as quick as possible (limiting amount of air), transferring the stuff into a smaller precision-drip bottle (despite a metal drip tube this time, it still clogged and wouldn't clean out despite all kinds of tricks), and even experimenting with all different consistencies of CA glue (super thin vs. medium viscosity vs. gel) to try and find one that would "last" longer - I think you get the idea. My advice would be to buy the smallest bottle you can (generally the cheapest, anyhow) and that way you'll have less go to waste. I no longer buy larger repackaged bottles from hobby stores, or even specialty hobby brands like Zap-A-Gap, since they all come in larger containers and are all essentially the same thing - pure cyanoacrylate glue.
In terms of usage, the gel variety (Krazy Glue Craft Gel, "Gap Filling Formula" Zap-A-Gap) has a longer set time (30-60 seconds) and is good if you need to position a part before the glue hardens it in place - another fringe benefit for assembling models or figures is that the gel variety also fills minor gaps due to the thicker consistency. Super thin CA glue is great for narrow spaces and has a quick set time (5-10 seconds, usually) - it makes the best use of precision applicators and allows capillary action to "draw" itself into narrow crevices due to the surface tension of the liquid CA glue (in other words, if applied to a narrow crack between two close-fitting held-together parts, it will creep in between the parts and join them in a very short time frame. Medium viscosity CA glue behaves, well, somewhere in the middle.
A lot of people use CA bond time accelerators or "zip kickers" - now while I've never personally bought them, I've likewise never had reason to. The idea behind a CA accelerator is that it essentially serves as a catalyst for the glue's "chemical reaction" - in other words, it increases the amount of moisture in contact with the glue so that it sets quicker. As I mentioned at the start, the key feature of CA glue is that it responds extremely well to moisture of any kind - unsurprisingly enough, even a drop or two of plain water will cause your CA glue to "kick off" immediately when compared to allowing CA glue to draw moisture from the to-be-glued parts and ambient humidity. Even breathing on setting CA glue has much the same effect (with the down side of potential inhalation of glue fumes), while using a hair dryer on parts glued with CA adds funneled air moisture via the directed blower as well as a quicker evaporation rate. You can likewise add a great number of materials to CA glue besides water that have a high "moisture" content and a fast evaporation rate in order to speed up the glue's chemical reaction: acetone, mineral spirits, rubbing alcohol, Tenax 7-R, thin viscosity plastic (polystyrene) cement, and even Green Stuff (AKA Kneadatite) - you'll find that the CA glue sets up much quicker, almost instantly in some cases. The greater the added moisture coupled with a quicker evaporation, the faster the setting time. (Again, I've never bought a "name brand" CA glue bond time accelerator - but I've used plenty "off-brand" kinds!) A few notes on this subject: a lot of chemicals are almost as toxic on inhalation as the glue fumes itself, so be careful, and using some sort of "zip kicker" versus allowing it to "naturally" set results in a weaker join - a forced reaction means less opportunity to spread or establish stronger polymer bonds.
One thing about CA glue to always keep in mind, is that even though it make have set visibly and bonded parts together physically it is by no means "dry" (although technically this is true about most substances that start out "wet," like paint or even spray primer.) It continues to give off fumes until completely evaporated and these fumes are lighter than air. If you have CA glue inside a sealed container (like a glued-on enclosed canopy or glue-fastened vehicle cockpit, for example), fumes from the drying CA glue will interact with ambient humidity inside the container and you will end up with a hazy coating everywhere that the fumes have spread - great for "tinted glass" effects, but not so good for a clear plastic window. Like it says on the bottle labels, always use CA glue in an open, well-ventilated space: I'd suggest that when allowing CA-glued parts to dry, you should lay them or prop them up so that the fumes have somewhere to vent away other than inside your model.
In a roundabout way, this brings me back to the problem of preventing clogged glue bottles. The reason they clog or get their lids glued on solidly is the "reacts with moisture" part - after you put the glue bottle cap on, the glue solidifies as it reacts with ambient moisture drawn into the mouth of the glue bottle as well as any moisture on the outside of the bottle opening or inside the cap itself. You're essentially putting a self-sealing cork on your glue bottle if there's any glue in the opening whatsoever, and it will happily adhere the moisture-laden bottle cap to the moisture-laden bottle mouth if you let it - I speak from experience here.
Here are several methods to minimize your CA glue bottles "clogging" themselves and becoming unusable as a result:
- Make sure to wipe any excess glue off the opening of the bottle, in order to minimize the amount of chemical bonding after you put the cap on.
- Use bottles with a smaller opening, or better yet, smaller bottles outright - the smaller the opening and the smaller the amount of glue left behind to react, the easier it will be to break the seal the next time around.
- Accept that the glue will eventually seal its bottle shut, buy bottles with long "spouts," and simply snip off the blocked end whenever it happens.
- Coat the open end of your glue bottle before putting the lid on with something that A) does not carry moisture and B) will help to protect the glue inside from additional moisture - smearing a little bit of petroleum jelly (Vaseline) on the mouth of your glue bottle will keep it usable much longer and help to prevent clogs.