I have submitted a manuscript to a journal and it is currently under review. I have also written a second manuscript which is essentially an extension of the first manuscript. The first manuscript mainly deals with establishing baseline behavior while the second manuscript deals with expanding the results of the first paper by considering additional conditions. The problem formulation, literature review and solution methodology are the same with only minor changes.
In such a situation, should one rewrite these sections or paraphrase from the first paper? The results and discussion stand on their own. Since I am working full time in the industry now, I am not aware of how I should deal with this. My advisor from my Master's degree is not helpful. Is there any advantage to submitting the second manuscript to the same journal?
For reference, the manuscripts related to deals with numerical simulations.