As far as painting the body, painting itself takes little skill until you get into airbrushing. All it takes is patience and care when masking and a plan of which colors to lay first. Always go darkest color first then lighter and lighter colors in your progression through the paint scheme. As stated above, your translucent paint would have to be laid down last.
90% of a good finished product with a paint job is prep and masking, which can be done over and over until it's right before you ever break out a paint can. You need to thoroughly wash the body to start. Not just to make the paint adhere, but also so that your mask sticks properly and doesn't lift while painting causing bleed through. As a final tip, when spraying translucent or candy paints, I hold the body up to a light so that I can easily see that I'm laying down an even coat.
Six months ago you could practice on protech bodies for about $15 a piece, but now they're getting scarce so I would practice on soda bottles.

Box art bodies are deceptively difficult, but the difficulty lies in finding the right color paint and properly taping off the stripes correctly. Pushing the button on the top of a spray can is the easy part.