we've rubbed all paint off the car.

Marcia, I think a little more information on what you are trying to do will help us reply.

hand rubbed back to base.body is done.yep seams are showing.blocked as we went.all straight,just want to know what first coat qwe need to use be for primer.

If the seams are showing but the car was blocked, I'm assuming that there is no bodywork to be done and you didn't break through the gelcoat to raw fiberglass? If that's the case, I would start out with a good epoxy sealer, then a high build primer. The epoxy sealer is expensive but good insurance to protect a good paint job from and residues locked in the fiberglass. The high build primer will fill in a lot of the smaller imperfections...

I agree exactly.  Start with a quality epoxy primer, then a few coats of high build primer.  Then block with a long board, then more high build primer.  Until you think your arms will fall off.  Then mist a light coat of Krylon in some contrasting color over the whole car, and block with 180 grit on a long board.  You will be amazed at how many flaws you will find.  Doing it once will give you a pretty nice paint job.  Doing it several times will give you a stunning job.  Invest as much time and effort as you want.

Good Luck
Larry