"put a low value (2-47 ohm) high wattage (2 - 5 Watt) resistor inline"

There is a hole in the roof. It is raining.
1. Put a container under the leak. (or)
2. Arrest the leak.

Yes yes, I know you cannot climb on the roof when it is raining. So do the first. Then when the rain stops do the second.

The resistor to drop voltage will shift the heating from the 7805 to the resistor and the drop will depend on the load. A last resort solution. Best would be to re-order the transformer with a reduced secondary.

Raghu