If your snake is having problems shedding make a moist hide for him.
They're very easy.
1) Get a margarine (or any plastic) container
2) Cut a slit in it for snake entrance,
3) Soak some sphagnum moss, wring it out so that it's damp but not wet
4) Place the damp moss inside of the plastic container and put the lid on
5) Place the container inside of the snake's viv
This hide is only necessary when your snake is about to shed, but you can leave it in there as a permanent hide if your snakes really like it. Just make sure to keep the moss moist, replacing it when necessary.
Also, please note that if you do not have a moist hide its not like your snake will have problems shedding. Snakes have a HUGE threshold for humidity. I think it's somewhere from 10-80% that they're okay with. If your snake has problems shedding though, as in the shed does not come off in one long piece, this can be a way to ensure that your snake will have a good shed the next time.