Unless you fermented it for several months there should be plenty of yeast still in suspension to bottle prime, even after cold crashing. If you do add yeast, you only need a tiny bit, not a whole packet. I'd advise against using a wine or champagne yeast in the bottles, because it will not only consume the priming sugar, but will also eat the more complex sugars left behind by the original yeast, and could likely result in bottle bombs. 4 volumes is already pushing the limits of standard bottles, it would only take a little more before you'd have a mess on your hands.