A couple of thoughts.
One I think that might help is saying, "It's really quite easy when I thin about it." Or, "I'm sure I'll find the easy solution"
As for imagining pain turning into smoke and leaving the body. Consider this.
Have you ever had a problem and thought "wouldn't it be nice if I could just rub a magic lamp, a genie pops will pop our and make my wish come true"? Or something like that. To image that you didn't really see a genie, or a magic lamp that you rubbed (and there might have been smoke in your imagination). What you did was remember images that you saw and created that image for a split second.
Now don't think of a polar bear wearing a pink and lime green polka dotted bathing trunks (not bikini). Did you smile, some might snicker but guess what! You imagined it. I don't think I've ever seen a picture of a real polar bear in swimmers, have you?
So when you look for an image of pain turning into smoke. You allow your mind to create it. It lasts for a split second but that's enough. Like Chunyi Lin says, "imagine" And then forget because ultimately you're heading into the emptiness. So when Chunyi suggests that you imagine, he has offered something useful to think about if you're going to be thinking on your way to the emptiness. 
Whatever the mind happens to focus on for that split second is fine, when you hit the emptiness another part of your mind is looking after that anyway.
Alex
