Painting a car's bonnet requires a lot of preparation and then a clean, dust-free environment for the actual painting. If necessary, build a simple enclosure with walls made from draped plastic sheeting that is big enough to hold you, your car's bonnet and your spray painting equipment.
Remove the bonnet from the car and place on a secure level surface.
Remove any chrome or emblems, if possible. Use masking tape on any chrome, emblems or rubber that cannot be removed.
Sand with 320 grit sanding block. Sand in the same direction as much as possible. Sand thoroughly down to the metal. Make certain any shiny areas of clear coat and/or old paint have been completely removed. Use 320 grit sandpaper on any areas that are too small for a sanding block.
Wet a Scotch Brite scouring pad and do a final rub down of your bonnet. Go over the entire surface with a wet Scotch Brite pad, rubbing in the same direction as you did with the sanding block.
Rinse your bonnet thoroughly and dry with a chamois or a soft cotton towel. Inspect every square centimetre looking for any clear coat or old paint. If you find any, sand with the sanding block until completely removed. Wipe the entire bonnet down with tack cloths and move it into your dust-free painting booth.
Spray a light coat of primer onto your bonnet. Keep the sprayer moving at all times and try to keep the spray as even as possible. Allow the primer to dry and then spray on another very light coat of primer. Allow to dry thoroughly. Spray a coat of car paint onto your bonnet and allow it to dry completely. Then wipe gently with 0000 steel wool. Wipe down with a tack cloth and spray a second coat of paint. Allow to dry.
Spray a coat of a clear coat on your bonnet (keep the sprayer constantly moving and spray as evenly as possible) and allow to dry. Wipe gently with 0000 steel wool. Wipe with a clean tack cloth and spray a second coat of clear coat. Allow to dry. Gently wipe with 0000 steel wool. Wipe with a clean tack cloth and then spray on a third coat of clear coat and allow to dry. Your bonnet should now look show room perfect.
When polishing between coats with the 0000 steel wool, be gentle and rub lightly in a circular motion. When using a tack cloth between coats, always use a new cloth each time to avoid the possibility of micro scratches in your finish.