Nothing wrong with using a rattle can. I started out all my armour that way, and if I'm doing a vehicle that is overall OD, I still use a rattle can sometimes, as it's easy and quick to do.
Couple of things to remember prior to spraying:
1) Do it outside. It'll kick up a lot of paint in the air, and you don't want to inhale that
2) Shake the can very very well
3) If you wish, you can place the can in a tray of mildly warm water for a few minutes, as it will 'soften' the paint and allow it to flow more freely.
When you do spray, start off the model on one side, carry over the entire length, and end off model on opposite side. This is the most efficient way to get a nice, even coat. Make sure not to idle, as the paint will pool very quickly from a can.
Have fun, hope it works out well.