Depends on a couple things I think? If you painted heavy coats, it will take a long time for the paint to cure.I'm guessing this is an enamel based paint? The other problem might also be colder than average temperatures.If it is relatively cold the paint will have a hard time curing and it can and will stray sticky/tacky for days.Also, elevated humitity combined with temperature will mess with paint curing.All these elements can wreck havock on painting.
Best thing to do before painting(and I apologize if I am repeating information you are familiar with) is to really shake the hell out of the can(a good 5 minutes of vigourous shaking),then soak the can in very warm water.I usually heat a pot of water on the stove to about 120 deg. As long as I can stick my finger in it, the water isn't too hot,then remove the pot from the burner and stand the paint can upright in an open zip lock and soak the can in the water to heat the paint up for a good 5-10 minutes.This will improve the paint flow when spraying. Then after that, give the can a really good shake before painting (another 3-5 min).Paint your part/object/model(whatever it may be) in the garage or outside if it isn't raining(garage is best if you have one).
Do a couple light coats (remember to give a good 15-20 minutes between coats in cold environments).When you are done painting,let your model sit in the garage for a good hour, then if you can stand it...bring it indoors.It will stink your house up some, but it is the only way to get the paint to dry in a relatively reasonable amount of time.Hopefully your house/place will be at least 65deg inside. It should be dry to the touch and *tack free* in about 24 hrs.Bonus if you can keep the indoor temperature warmer,it only helps move things along.