The main thing with spraying is technique and as has been said cleanliness. spray tins are ok for small jobs, but for the likes of the bonnet i'd try and source an oil free compressor.
There are loads of guides available about bodywork and painting techniques, but the main thing after all the prep work is smoothness of the movement of the spray gun at a steady distance and correct application thickness of paint, too much and it'll run badly and look cack, too little and youll remove all the paint when you come to sand for the next coat!
Several thinner coats will give a far better finish than one thick one.
You'll need a wide selection of wet/dry papers and sand from the coursest to the finest when removing the old paint.(you don't need to get it to bare metal, take a couple of layers off and then clean it de tack it -special cloth- and use pannel wipe, let it dry then prime it let that dry smooth it down with fine paper, de tack it again, prime clean detack then paint)
When al the painting is done (same sort of thing as with the priming) let it harden, flat the paint down as before, really clean it off again, and a few coats of laquer can then be applied one after the other in whteever interval the paint tin reccomends. Then use some buffing materials to get a mirror shine once the whole thing has hardened (depending on the type of paint used the techniques may vary slightly)
Once the laquer has hardened for a week or two you can then wax it with a good quality wax like meguiars
Hope that helps.
Just have a go if you can bear having a dodgy looking bonnet for a bit. Oh and to do this properly it'll take a good few days, so no putting the bonnet back on the car inbetween coats to pop to the shops