Painting with rattlecans

My first advice would be to only use flat colours. But I have managed some decent finishes with cans and metallic paint.

If you can find one, get one of the plastic handles that let you use the can as a spray gun. It makes it easier to get a decent finish. Practice if you can on a bit of scrap.

Shake the can a lot. A lot more than you think.

Apply in long spraying strokes starting the spray before the panel and not stopping until the spray is clear of the panel. Move the can parallel to the work. Don't do that silly waving the can around in a zig zag like graffiti artists do. If you are too close and apply too much you will get sags and runs. Too far away and you will get a rough stipple finish.

Cleanliness, lack of wind if working outside helps.

If it all goes wrong you can remove it, prepare the work and start again.

If you are too close and apply too much you will get

That's the hardest bit to get right. You need it 'wet' enough to get the paint to flow, but too much and rattlecan paint sags really easily.