Even Lorraine Massey was conflicted and a little wishy-washy about thermal drying w/the CG routine. First, she militantly decreed that hair dryers were death to hair (She called them "hair fryers"). Then she switched up her position and started making big bucks off of her hand-shaped dryer contraption.
What seems to be true for most curlies is that the less heat you use, the better off your hair is. There are plenty of people who get away with regularly using a diffuser or a hooded dryer. If your hair is generally in good shape, you can use the "warm" setting on either of these gadgets until hair is about 70-75% dry and your hair will probably be just fine.