The "24 hour" number refers to the recommended minimum time between printing and coating. That's really just a ballpark spec. The drying time is greatly affected by temperature, humidity, and air circulation. As a general rule, you can apply the next coat as soon as the last coat is feels dry to the touch. Here in the high desert, I find 10 to 15 minutes between three thinnish Glamour II coats is about right.
Glamour II, amen! If you're a newbie, it gives you the highest probability of success.
Spraying is the best option if you have a place to do it. Have not lost a canvas to spraying issues in a very long time. For certain canvases like the glossies, spraying is the only option. If you notice your roller is getting dingy looking, you need to spray. Those Wagner guns are OK, but the filters
suck could use improvement.