How can I portion out frozen cookie dough?
Thaw in refrigerator until soft enough to portion.  Portion total batch, then re-freeze. Ideally, it should have been portioned before initial freeze. At this point, unless you want to bake them all, you will be fine with a refrigerated thaw, portion, and re-freeze.  Store portioned, frozen, cookie dough with as little air in the container as possible.