Trying to confirm whether or not once you get a pet grandmastered, can you use that pet's grandmaster primal with any warder you have active or just the one that it was grandmastered on? If you read through the eq2 wire info, and follow the links Feldon provided back to Whilhelmina's original info its stated that you can use the grandmaster ability with any pet.
That's correct. The primal for maxing their affinity can be used while any warder is out. They are limited to specific stances though of course.
Slight correction, depending on whether their primal is spiritual or feral, you must be in that stance to use their primal.