SMOKE EM UP Challenge is a trifle tricky... wut wut... HELP PLEASE?

[Ban Junky]

Can anyone offer practical help and advice on how to get more success in this challenge please?

I am currently working through the Tactical Challenges and I am finding it rather slow going getting through the SMOKE GRENADE one...

The challenge is to kill an enemy while they are in your smoke...

I am doing it but it is taking me a long time relative to the others...

I throw my smoke in to a Drop Zone, or on a Flag, or at a Choke Point, then follow it with a Semtex sometimes this works but other times I will get a kill that doesn't count...

Anyone know if there is a time limit, or radius or something?

Also any suggestions from those that found a good way to do it would be great?

Thanks for any help...

[SeaBass]

The easiest way I've found to complete this challenge. Is to equip a weapon with thermal sights. As long as they are not using Assasssin they'll glow bright white in your smoke.