I'm not sure if this is still of any help, but S&B is my solution to rootless orchids. Its also what I use when I bought bareroot orchids in the middle of winter. It never failed even when the plants have to stay in the bag for months. No mold.

1. What I do is to use all new materials including the bag.
2. Clean the plant thoroughly and rinse it with fungicide solution before putting it aside to dry. Dust the base of the plant with fungicide powder for extra protection.
3. I then soak the sphag with the same fungicide solution and squeeze some excess water out.
4. I usually put the plant in an empty plastic pot also rinsed with fungicide before putting it in the bag to prevent the plant from getting in direct contact with the wet sphag.
5. I use a bag that is big enough to make a "tent" when I blow air into the bag before closing. Open the bag every few days, inspect the plant, re wet the sphag if necessary.