Well snake,
I've done this with my S-3 Viking. Although I flunked the kit itself - in my opinion - I did get the smoking done right.
I used the tamiya smoke, that you've got as well.
Firstly I got dust in the airbrushed layer, that made me get the paint of again.
Painting your canopy has to be absolutely perfect and smooth. Any 'petite' flaw shows obviously.. So, clean your spraybooth.
Secondly, spraying the smoke on, should turn out in a perfect smooth layer as well. A problem I came across is the orange-skin-effect (transtaed from Dutch, hopes it makes sense to you). This might be solved witth a layer Future over the dried smoke.
What I did was when starting to clean my airbrush with alcohol, spraying a wet coat of alcohol over the just painted layer of smoke. Ofcourse make sure the alcohol is clean. Otherwise your previous painting sessions mingle int your canopy. The alcohol all makes it blend in smooth.
Three things:
1. don't spray too much paint, is easily gets too dark
2. don't spray too much alcohol, to prevent it running and dripping, making ugly stains.
3. Spray the pure alcohol from a distance and under heavy pressure. Otherwise you'll spray the fresh paint away.
It might take you a few times perfecting it. I propbably cleaned the canopy five or six times completely until it worked out okay. In the end, my canopy of the Viking got too dark. So, too much smoke sprayed on. Flunked the kit anyway, so it doesn't matter.
"Next time, gadget, next time.Miauw...."
Look at my S-3 on:
http://m.1asphost.com/svankreijl/svankreijl
section: built models, S-3 Viking.