1200-1500 is exactly what you want to finish off with, the acid etch primer will adhere fine to a smoothed surface.
I started off with 80 grit to get into the top layerr of lacquer/paint and then progressively worked my way upto 1200 to finish off.
What i would say is once i had a decent finish the 1200 was done as a wet and dry process, it helps get the perfectly flat finish. This is where nearly all of the prep time is spent and you need to keep checking the finish is spot on. After you've finished flatting/wet and dry sanding the final primer coat there's no going back when you put the first colour coat on, it'll show up any scratch surfaces that you didn't smooth out properly.
Just take you're time and if you start to think you rushing the job, walk away and leave it a little while.
HTH