To add humidity to the microclimate around your plant, get a saucer/dish and add a layer of rocks in the dish. Pour some water over the rocks, and set the plant on the dish. The rocks are there to hold your plant up and out of the water.

I do this, especially with my orchids but it's never enough. I don't have room to do this to my whole sun room so I also group plants together and it's still too dry.

How about a humidifier? Cheaper in the long run, you never run out of solution, and it is better for your plants. I can't imagine clogging stomates that plant need to use for Ps, could be good for your plants. I am also surpirsed that you fare having that big of a problem in MD, where it is fairly humid as it is...

I have no problem in the summer when they can all go outside, my cocao is loving it!

But the problem is when I have to bring them in for overwintering.

A humidifier would help but the room is pretty large, and my mom doesn't want one running just for the plants :(

My answer is

NO, I definitley would not use it.

I think you should call the company and ask some specific questions about this particular use of Wilt Pruf. It is very commonly used on indoor plants, but not necessarily to prevent protection from lack of humidity. (It prevents transpiration, which is not something you might want to happen to your plants all winter long!)

When you call them, be very clear about what your needs are and have a list of the plants you intend to spray. I absolutely would NOT use this product unless you had a guarantee of safety for your plants. I can tell that you are hoping this will be the answer for your problem, but don't take any chances.

Here is a link that might be useful: Wiltpruf

Yes, I was! Atleast until I have a greenhouse to put them in. I will call them, thank you for the advice!