Rose

The main bit of advice I have for painting with aerosols would be to warm the can(s). This enables the paint to be atomised finer as it passes through the nozzle, which results in a better finish. Bare in mind I said warm, DO NOT overheat, you are taking the chill off the can, not risking losing a hand due to an aerosol exploding while you hold it.
Make sure you give the can(s) a good shake before using them. The best technique for painting with an aerosol is to use light, overlapping strokes. You need to leave at least 5 minutes between coats to give the solvents in the paint time to evaporate. This time can be cut by using a hairdryer. I would recommend either wearing a mask or going outside for this next bit, the vapours can be dangerous.

First apply the plastic primer, I would highly recommend you use this as it will give the paint something more to stick to than just the light ‘key’ scratches. You could skip the plastic primer stage, but if the part gets chipped the paint will start to flake off.

You may need to apply 3/4 coats of plastic primer, but you can use a hairdryer to speed the process of drying. Remember, a light coat often is better than a heavy coat less often. Plastic primer is generally quite thin, so be careful not to get any ‘runs’.

Once the plastic primer is dry it’s time to apply the basecoat. Again, use light overlapping strokes. Depending on the colour, it may take anything from 3 to 8 coats to cover. Again, make sure you leave enough time between coats.
Once the colour has completely covered the part, you can start to apply the lacquer. This is not a necessity, but it helps to protect the basecoat and adds a shine (if you chose gloss lacquer).

Apply this the same way as the basecoat gradually building up the thickness of the lacquer. You’ll probably need about 4 or 5 coats of lacquer.

Leave the part for a good 3 or 4 hours before you try to polish and re-fit it. There is nothing worse than marking fresh paintwork.

Good Luck