Shedding issues are almost always a husbandry issue. (disease, parasite and starvation aside) fix the husbandry and the issue will correct. No gimmicks needed, if the humidity is bought back to correct the snake will complete the shed on its own.
If you choose to use the pillow case method be sure to choose a poor quality one or better yet a snake/scallop bag that will not be air tight when wet. high count cotton can swell and be very difficult to breath through. I would suggest a tub with a wet towel in the bottom.
Easy fix. Get a plastic tub with a lid. Cut a couple holes in the lid. Fill up a few inches with warm water, but the boa shouldn't have to swim to stay on surface. Let the snake soak for ~30 min. Take a damp towel in your hand and wrap around the snake, letting it slither through your hand as you apply LIGHT pressure. This should remove most of the shed. I live in Colorado where we have super low humidity. I soak most of my boas when I notice they are in shed. If they have a few soakings under their belt the shed usually goes great. You can also provide a humid hide when they are in blue. Easy to DIY with a tupper ware container and some damp sphagnum moss.