"if you must, wear gloves, drape a big rag over the rad cap, and prepare to still get burned."
Excessive pressure would lead me to assume your pressure cap is not releasing properly at 14 or 15 psi (or whatever your particular cooling system is designed for). If, however, you had coolant routinely blasting out the vent for the pressure relief cap, then I would assume some other issue. There are lots of hidden places that your coolant loss could be going and not necessarily related to the pressure of the system.