What's the best way to change the radiator?
 

I want to change out my left and right radiators. They were never cleaned and when I did it I discovered all the junk rotting into the corners. Is there a special method I have to use to 'prime' the radiators once I swap them or can I just follow the fluid change procedure and refill from the overflow tank.
Thanks,
Chris

EDIT: The main reason is when befoer I cleaned it I detected the antifreeze smell. When cleaned the dirt did smell too. I ran the car at temp with the radiator hanging there and there were no obvious leaks. I can still get a wiff once in a while too. My coolant level is not going down fast (takes months before I have to top off).

Here's the procedure for bleeding the system.
 

• Start with a cold engine.

• Remove both caps (oil and coolant).

• Pull bottom plastic cover out (using a spatula lift one edge and pull out).

• Lift bow on bleeder valve. Screw oil cap on again.

Note:
On Tiptronic vehicles, the pneumatically operated coolant shutoff valve (flat-seat-valve) must be opened for the bleeding process. The electric switch-over valve must be switched off for this purpose.
Triggering can be performed with the PST-2 or PIWIS, or by pulling out the Tiptronic control module fuse B1 with the ignition switched off.

• Check whether coolant shutoff valve is open.

• Fill reservoir with coolant up to the bottom edge of the filler neck.

• Run the engine at idle and top off with coolant until no more coolant flows into the cooling system when the engine is revved moderately. (Coolant level now at the lower edge of the filler neck) The coolant temperature must not exceed 80 degrees Celsius; proceed directly to the next step if necessary.

• Close the reservoir and warm the engine up to operating temperature at an engine speed of 2,500 rpm until the thermostat opens (approximately after 10 minutes). Coolant temperature should now be 90 degrees Celsius.

• Check: The radiator supply lines and return lines in the front wheel housings must be hot.

• Allow the engine to run another 5 minutes at 2,500 rpm. Every 30 seconds, briefly rev the engine to 5,000 rpm. This is important for proper bleeding.

Note:
The level warning light can light up during the bleeding process (reset by restarting the engine). Interrupt the procedure if the coolant level is below the "MIN" mark. Open the reservoir with extreme caution and allow overpressure to escapeuntil the coolant level reaches the lower edge of the filler neck; top off with coolant if necessary. Again, intermitently rev the engine for 5 minutes.

• Allow engine to run at idle speed until any activated radiator fans switch off again. Then switch off the engine. Open reservoir cap with extreme caution until the reservoir is depressurized (danger of scalding!).

• Top up coolant expansion tank until level reaches lower edge of filler neck (cold, this corresponds to = "MAX").

• Reposition bow on bleeder shutoff valve. Unscrew cap.

• Put on cover and body seal. Screw on both caps.

• Reactivate ATF shut-off valve on Tiptronic vehicles.

Happy Boxstering,
Pedro