How to transition from smooth to textured food?

To those mummies who did/does TW with your infant, how do you transition from smooth textured food to textured food like porridge? My infant is 8m10d old and I want to transition him from cereal to porridge but he gagged and sometimes threw up. Transitioning him slowly since I read that by 9 mths old should eat textured food already. I did porridge for him last time but I made sure to blend it smooth before feeding him and he ate it well. Advice needed. Greatly appreciate your help!