humidity while drying

a friend has 4 plants that he is about to dry in a small basement room..it is cold and damp in the room but he has a oil heater and a dehumidifier..would it be ok to run both of these while drying the plants or will it cause them to dry to fast..he can maintain a temp of 65to70 and humidity at 40% or so..he just does not want them to dry to fast or to slow and mold

You want a cool dry dark space for drying, as long as its 50 or above I would just run the dehumidifier, a slow drying process is what you want, then for best results don't forget to cure!