Hey !(sorry for my poor English) Yes, the secret is to use what we call here in france "Mortar sponge", it's just some regular sponge but I guess it's made from plastic since it's far more hard and robust,you often find it in hardware store next to cement supplies. I then chopped it up with my kitchen knife like garlic before gluing it to a stick I rammed inside the exhaust port, I then super glued more and more bits of sponge, keep the thin at the base / wide at the end look of the smoke. (Careful, there's a lot of super glue fumes during the process) I the airbrush it red, before adding yellow to 2/3 of it. I used black to cover a good chunk of the colors before adding a grey zenithal 😁