im currently doing this mate. scrapped a wall right by the fog light so there was two deep scuffs either side of the fog light.
paint was £16 i think from renault
started by filling the holes. not too thickotherwise it would take days to sand down the filler put one spread on then used 180 paper dry to cut back the filler. put another spread on to fill in any more holes and repeat the sanding with the 180 paper.
work through the grades dry stepping up once you have got rid of the deeper scratches caused by the previous paper. I used. 180, 240, 320, 600, 800, 1200
should be tottaly smooth so mask up the sections you dont want paint on and cover as much of the car as you can to prevent overspray.
use a fan heater or a hair dryer to get the surface nice and warm before painting.
2 thin coats of primer 15-20mins apart. leaving the heat on it during and after each coat. once dry you can hit it with some 800dry 800wet paper then 1200dry 1200wet. clean off all dust and water then put on another 2 thin coats of primer keeping the heat on it while its drying. once dry a light rub of wet 1200 and you should be ready for paint.
make sure its clean and the surface is warm before painting. take your time it is very frustrating. spray too close and you will get orange peel, spray to far away and it will go on like sand paper. 2 thin coats using the heat all the time. allow to dry and go with some 1500 paper wet. 2 more coats allow to dry then 2000 wet sandpaper it.
you will have to feather it in so you dont get lines where you have masked up so hit the line with some 1500wet and spray over the line a bit.
lacquer is the harderst part. 2 thin coats. 2000wet then another 2 thin coats. allow to dry then use some farecla g3 rubbing compound. once you have finished with the compound you will be able to see if it need more lacquer for added shine. another coat of lacquer allow to dry and g3 it again.
its very frustrating but will save you a lot of money compared to having a respray. use a ventillated area or you will have a headache now like me after spending 3 hours of the night doing the above process in a garage.
Alex