There is no need to prime if you are using flat MM enamels. That is your primer. If you see anything rough after first coat you can sand and then go back and hit it again with the same color.
I have this big kit. It should be a lot of fun. GMM makes 1/200th P/E railings if you're interested.
If I were going to build this kit I would prime with MM enamels then use Tamiya acrylic for the yellow, rust red color , and gray. In order to weather with oils. The Tamiya is completely resistant to oil wash weathering.