That said, I would do just as you wrote, prime, take a look, and then work those areas that specifically need attention. I've had best results with two coats of the high build then sanding. You might try that misting thing Joel has been doing on the FS14 thread. It seems like a great way to really pick out the problem areas.
1) Use straight edges with a light behind it to look for a fair surface. The light will show through between the hull and the straight edge if it is not fair.
2) Position a strong light close the hull surface. Step 6 or more feet away from the hull and look right down the side (block the light with your hand while you can still look down the hull). This will show many imperfections if they exist.
The above doesn't take very long and will tell you if you are ready.
Resist the urge to forge ahead if you have doubts that you are really ready for the next step.