Help! I went to bleed the air out of the radiator in my daughter's room (I just did the one in the bathroom with perfect results) and rather than a valve thingy that needs that weird bleeder key, these radiators have flathead slotted screws... a quarter turn usually works to let out the air. Well, the one in my daughter's room is stripped and won't budge, and I'm afraid if I do get it loosened that A: I won't be able to close it and B: If I go to replace it (hot water shooting out all the while) I won't have an appropriate screw to match it.
What do I do? It's freezing in there? Can I bleed the entire system from one point somewhere else?