However, I found a letter in this month's Delicious magazine asking about crackling and the answer was quite interesting. When asked about cooking crackling properly, Chef Richard Corrigan said the following:
The key to crisp crackling is to remove the skin, with the fat, from the meat. Salt both sides, then place on a baking rack in the oven.If you use a tray, the fat won't drip away and this will make the crackling soggy. Make sure you take all the meat off the skin too, as this could also make the crackling soggy. If your crackling is burning, the oven is too high. Ideally, cook the crackling slowly at 100C for 3 hours.
This makes interesting reading for smokers, you could get a skin-on shoulder, remove the skin and fat, and put it on a rack above the cooking meat. This way you'll get the fat dripping on the meat, basting it and if it's true that crackling cooks well at low temperatures you could get a nice bit of crackling as a bonus.
I've not tried this yet, but I will. Thought I'd share the tip so others can give it a go.