If you're going with a spray job 3-4 coats of primer - filler then the same of topcoat but sand between the primer and the top coat using 800 then 1200 .... you need to be smooth enough to remove the scratches but still leave enough for a 'key' into the primer for the top coat.

just get rid of all dust in the work/spray area. 90% of your time will be getting to where you start your colour.

I just finished spraying my coupe this week actually. I did it in white Acrylic. started with rattle can etch primer after all rust repairs. 4 coats of high fill sanded back with 800g, 2 coats of primer sanded back with 800g, 4 coats white acrylic sanded back with 1200g, 4 coats acrylic clear sanded with 1200 then 2000. Still need to buff it but will do that when the car is ready to be put back together.

I used a pop up marque from kogan and honestly spent more time repairing it after all the wind i had over the last few months.

I'd recommend spending the time making a decent area to spray it first.

Things i found really helpful when spraying were to back of the mixture or flow of paint, limited the amount of wastage and over spray to sand off.

I used paint from a local body repair shop but found the Septone products from supercheap auto to do the best job.