A/C condenser previously removed

Don't even think of not pumping the system into a vacuum. Even though the ends of the tubes were plugged, air has still gotten in the system, along with the humidity in the air. If you just start pushing refrigerant into the ports, where is that air and moisture going to go? It will still be in there where moisture combines with refrigerant to form an acid that will corrode the condenser and evaporator.

The reason we always pump the system into a vacuum is at a near perfect vacuum, water boils at 77 degrees Fahrenheit. That means it turns to a vapor that can be drawn out. The vacuum also aids in pulling the new refrigerant in. At a bare minimum, the system should be pumped for 20 minutes. Most of us prefer 30 - 45 minutes. When the pump is turned off, watch the gauges for a few minutes. If the vacuum drops, there is either a leak in the system, or there is still moisture in it that is vaporizing yet and expanding as it does so. If you see the vacuum dropping, evacuate the system for another 15 - 30 minutes, then check the gauges again. By this time all the moisture should be removed, so if the vacuum is still not holding, you'll need to check for a leak.