I had Portulacaria afra freeze with the leaves turning brown or falling off but I looked at the stems closely and found that some were still firm and some were shriveling and soft even though leaves were falling off, I cut off all the dead/soft stems and left the firm stems to see if they will grow new leaves. Same with sedum. If the stems were still firm I left them as is but if they were shriveled up I cut them back to the soil.
