i did the tailgate on my cab as that had some rust coming through in one corner, i did have to sand blast the rust out, grind and lose all rust, apply filler, allow to dry, apply undercoat, allow to dry, sand down, apply wet and dry.
preparation is a must, my first attempt i slammed the boot down on a wet towel and gave a lovely rag effect finish, second time needed more lacquer, third time bang on.
beneift of the MK1 is that the door seams, boots seams are wide and its angular shape knocks your eyes off the colour and its difficult to pick up colour changes on some parts do parts in sections.
my car is 15 years old i gave the paintcode to the paintshop mixed and it matched a treat.
bodyshops can give great results, i just dont have that kinder money at the moment and the last wannabe hero who sprayed my previous car must have been bladdered not one panel looked right.
give it a go or as mentioned by others do all the prep work before hand.