I am doing nonlinear buckling analysis for a stiffened plate on Abaqus. I apply compressive loads in a Riks step. However, before this step, I am required to create another separate step to apply out-of-plane lateral pressure such that once this step ends, the pressure will be kept constant during the following Riks step of the compressive load. 
My question is, should I use a general static step for applying the pressure? How to make sure that the pressure value will be kept constant in the following step?

Thanks