No, you didn't mess up by choosing a spray can. This ship...
/forums/514057/ShowPost.aspx
...was my first ship model and my first model in 15 years. The red, white, buff and some of the black are not only sprayed on from a can, but from Wal-Mart house brand cans that go for under a buck!
I got the confidence to use a Wal-Mart can from this thread:
http://www.finescale.com/fsm/community/forum/topic.asp?TOPIC_ID=37406
The tips the others have offered here are all great, especially the one about practicing with a milk jug. Go buy a cheap Wal-Mart can and practice. Also, warming the can changes everything, so stick it in war water for a couple of minutes.
Here's another tip: Prime EVERYTHING that you spay. No exceptions! Primer won't solve the problem you brought to the forum today, but trust me, it will save you a lot of sanding later. I had some horrible orange peel problems with this ship. I basically had to sand white paint off the entire hull because I shot onto it without priming first.