You should not be in a hurry to turn an open segment bowl. The rows do not get locked into place until there is a new row on top of it. If you do need to do some turning, avoid turning the top row because it is not locked. Once you add a closed segment ring to it, the entire bowl will turn like it is a closed segment bowl.
If you are using a gouge, always turn towards the bottom of the bowl. If you turn away from the bottom of the bowl, you are putting upward pressure on the segments which is doing its best to pop them off the turning.
So if you have to turn the bowl because it will be difficult to reach the bottom, only turn the inside and start from the row beneath the top row and turn towards the bottom of the bowl.
When it is time to turn the outside, you want to leave as much mass at the bottom of the bowl as possible so start your turning at the top row and work downward.
Remember that an open segment bowl is fragile by nature and if you remove mass from the bottom, the lower rows may not have the strength to hold the bowl together.
To get better at this, make open forms with just a few rows. Put a closed segment row on it and start at the top and you’ll have no problem at all. It is up to you whether you want to start with the outside or the inside but experience tells me that turning the inside is the biggest chance for failure so I tend to turn it first while I still have the mass of the bottom of the bowl in place.