I've taken six workshops on Lymphatic Drainage techniques from 6 different instructors, approximately 70 hours in all. Two of the seminars were through Upledger (Chickly's curriculum). I also teach an intro class in lymphatic drainage techniques.
Proper lymphatic drainage techniques should not be painful; and, except in a few areas, the pressure is barely enough to prevent the hand from sliding over the skin.
Valid research has shown that "extreme" pressure is not only ineffective, it CAN damage lymph vessels and lymph nodes. Vessels, fortunately, can generally repair themselves. Lymph nodes, however, can be damaged beyond repair! By all means, run from someone who uses "extreme" pressure over lymph nodes.