Read WARNING at top of this section. I have received several in response to want add I've posted. Different "members" but essentially the same. Get PM saying they have a friend that has what you need and gives you his email address.
Where I live, what I prime with depends on humidity. On a really dry day I'll use 4f but the finer the granulation the faster it absorbs moisture. I even have 7f ( think black talcum powder ) that almost instantly turns to tar most days. I use 3f most days and it works fine.