I wrote this yesterday in your thread.
The fastest for the moment could be to use existing textures (you could find sites with CC0 licensed textures), and with time, to try sculpting and procedural texturing (including imperfections, decals, etc…).
Regarding the rendering program, test them and see which one you like and which feels right for you. If you get into Blender, then see what Cycles or EEVEE are like.
Maybe Twinmotion. You can try their trial version without being pressed by time.