For maximum vibrancy stick with 100% GII Gloss and put down coats that still look wet when you walk away.
Note that GII is a water based product and theoretically can not be shipped in freezing weather, although my rep at BC says the gloss can survive a freeze/defrost cycle whereas the matte version can not. I'm a little dubious about that and I always stock up in September.
For those in northerly latitudes, it is possible to spray GII outside in surprisingly cool temperatures. I have gotten not just good but truly excellent canvas coats that were sprayed while I was standing on snow. You need at least mid 40F temps and watch out for condensation water drops from areas around the nozzle. The art should be taped up on a backing like foamcore and don't take the art or the spray gun outside until you are ready to spray. Bring the canvas and backing back inside before outside temps reach freezing, but otherwise leave it outside to dry.
Even in such cold temperatures I keep the artwork in shade because if it is left in the sun the surface temperatures can quickly rise to over 100F in areas with heavy ink coverage, and that's too hot for coating! If you must spray in direct sun, turn the art so sunlight hits its glancingly at no more than about 30 degrees, even on cold days. Ironic, eh?