Not sure if my 2 cents adds much here but I was surprised that I reckon I did at least 4 applications and I still didn't have the grain filler up to the surface of the wood. Given that I must have sanded the body half a dozen times (I removed several failed attempts at staining) when I applied my acrylic coat later, I was surprised that even after two cans of acrylic I could still run a fingernail across and feel the grain lines.
So, for me - fill, fill, fill some more.