Is it possible to paint/spray paint cardboard so it looks like a powdery black metal?
Is it possible ? Yes anything is possible. The real question is can you accomplish this task as a novice. Again I believe the answer is yes. But it may take a bit of practice. I would recommend a spray paint. But to properly apply a spray paint it takes a little bit of practice. Common mistakes are over-spray (causes drips) under-spray (not enough coverage). I would recommend that you practice your spraying, paying careful attention to your distance from the object to be painted. I would also recommend that you plan on several coats allowing proper drying time in between coats of paint. You will find you will end up with a better finished look using several thin coats as opposed to trying to cover everything in 1 or 2 heavier coats of paint. Time and patience is the key to any quality job.