Slow drip is good, but don't leave them in a little bit of water so long they have a chance to pollute it. Also, you want the temp to match, so a too-slow drip tends to cool down the water.
Although today, the opposite might be true! Whew, it was hot here today.
For most fish, dripping for an hour is plenty. Just be sure to keep taking out water, too, to that the water in the bucket/bag is almost the same as the tank.