First off, get prepared. I bought some goggles and an air filtration mask at my local hardware store. The paint fumes can sometimes cause me to have allergies, so this is a must. Plus, when I don't use it, black paint sometimes comes out when I blow my nose. This is gross and can't possibly be healthy. My neighbors probably think I'm a psycho, but I like being able to breathe.
I also picked this magical device up at a local arts and crafts store for about 4 USD. It's made by Krylon and it's called a "Can Gun". It makes it super easy to prime large models or to prime lots of small models without your fingers getting tired. It's mainly a quality of life thing.
Lastly, I picked up a large, but cheap, lazy susan from IKEA. It's called a Snudda and is only 8 USD. You can pick one up here, although I imagine any cheap lazy susan would work. I use the Snudda to be able to spin my models as I prime them. It makes all the difference in the world when you can easily get to all the angles. It's also ideal for when you're priming only the lighter colors from "above" to get the illusion of shading in your priming step. I'll generally prime one large model or five smaller ones at a time.
As to technique, I first lay the model on it's side or back and then prime with the spray angled to come from the bottom of the model. This is sure to get the underside covered. I then flip the model to its front or other side and do the same. Lastly, I stand the model up and hit it from front, left, back and right. Sometimes with the cork I find that I need to come back after the model is dry and hit the base with another coat. The cork seems to soak up the paint much more so than anything else I've encountered. I make sure to use small bursts of primer from about 8-10 inches away. The can should be making a "pshh pshh pshh pshh" sound and not a "psssshhhhhhhhh" sound. Small bursts. Also, avoid humidity if at all possible. Humidity can make a primer coat a little "fuzzy" and textured. It especially happens with white primer. You can get around this by doing multiple thin dustings of primer and allowing the paint to dry before applying the next dusting. It's doable, but tedious. I tend to queue up things I know will need to be painted white and save them for a nice, dry day. I also try to prime a ton of stuff during the summer and fall to get me through the winter.
After all that, here they are... ready for paint! Before and after.