Does the car have a heater? If so, make sure coolant is flowing through it during warmup. It will keep the coolant circulating better than any drilled hole could possibly accomplish. If there is a manual valve or a petcock like some engines have, be sure it's in the "open" or "full hot" position. The fact that the temp gauge is going up tells me it's not a situation flushing will help- - - -the coolant is getting hot enough to move the gauge, but it's not flowing past the thermostat fast enough to prevent a temp spike.
BTW, if the coolant isn't boiling and forcing the radiator cap to vent, the engine isn't getting hot enough to do any damage. What pressure radiator cap are you running? A 7 PSI cap was probably the original equipment item, and that will allow the cooling system to go to 233 degrees at sea level before it boils.
Jerry
