Question about eliminating windows

I am still in the planning stage of my build and looking around at buses. I really like the look of the windows down the bus, which is why I want to live in a skoolie. I do not wish to actually take them out. However, I will need to black some of them out to cover walls that I’ll need to construct inside the bus. I’m thinking of spraying over the inside of the windows I need to with flex seal. Has anyone done this or can weigh in with suggestions for how you covered the inside of your windows for wall building? Thank you!!