well, it is something that is missing in jets.
Try this: http://www.regin.com/rcsmoke.html
Im not sure it that will work on jets, but I dont see why now.

I have also seen another way: People used Estes Rockets in
EDF aircarft. Put two of those on your wingtip, and you get the extra thrust
and a nice smoke trail Only problem with that is, they dont last long.

V