Buy one of those cheap children's colouring-in books to practice on, will help with learning to spray between the lines.
Don't use cheap kids poster paints, except on groundwork, you wouldn't put gravel in your washing machine/tumble drier would you?
You certainly can spray it, but it's more like pebble-dashing & won't help you learn how to handle hobby paints.
You can use cheaper non-permanent Indian-inks or food colouring to practice with, much easier to clean up, less likely to need HazMat conditions & SwiMBO will be happier.
Airbrushes were originally used by illustrators to spray inks, guache, & acrylics, key points their thin-ness and Opacity/Transparancy...
You should consider the best airbrush and quiet compressor you can afford, as 'running out of canned-air' anxiety is real & canned air gets very expensive quickly.
Once you had practice on paper, then use a scrap/range target/donkey/yard sale/dollar store plane/car/tank to practice with paint on your intended target.