Half-full? You might be able to do a mini-wash inside the bottle. Fill with boiled and chilled water, shake, let stand five minutes, and decant slurry into your starter wort. The trub should sink first.
You are going to use a starter, right? They'll need to be woken up after a couple months' hibernation, and you need to make sure the culture is clean (smell and taste your starter beer) before you pitch a whole batch.