Guys, I made this SP revelation!
I was toying around with cannon velocity, and found that shells were catching in the intakes when assigned zero velocity. so what I've done, is I have contained a cannon in an intake, so when it fires, the shell stay inside the intake, and if you enable tracers... You get a trail!
The smoke color and size are customizable by XML editing the cannon part. Just shoot the cannon, and you should be good! It's in the AG section. Feel free to reverse engineer in any way you like. Unlike the rocket smoke generators, this should cause absolutely zero damage to your plane!
(Warranty void if damage is caused)

(Warning: excessive speeds and G-forces may dislodge the cannonball. no worries! just fire again.)