right here's how I've done my engine cover, plenum, battery and brake fluid cover, plastic surrounds: 
  
  
what you need: 
  
sandpaper (medium and fine) 
colour cans (or spray gun) I used normal paint, not thermal, and it's fine for the above. Nissan burger comes off. 
primer (plastic primer preferred) 
lacquer 
  
  
1- sand down plastics with medium sandpaper 
2- first coat of primer  
(wait at least 30 mins) 
3- sand down with fine sandpaper 
4- second coat of primer 
(wait at least 30 mins) 
5- sand down with fine sandpaper 
6- 3rd coat of primer 
leave overnight 
  
following day: 
  
1- sand down plastics with fine sandpaper 
2- first coat of colour 
(wait at least 30 mins) 
3- second coat of colour 
(wait at least 30 mins) 
4- 3rd coat of colour 
preferaable many more thin coats of colour 
leave overnight 
  
  
then on day 3 
  
1- sand down plastics with fine sandpaper to get rid of shine of colour 
2- first coat of lacquer 
(wait at least 30 mins) 
3- second coat of lacquer 
(wait at least 30 mins) 
4- third coat of lacquer 
leave overnight 
  
  
NOTE: don't use too much colour/laquer in one go otherwise paint/laquer will run