trans cooler in/out ?

I had ordered a a new radiator from Be-Cool, and they instructed me to route it through the radiator first, and then the external cooler. They mentioned the bringing the fluid to engine temp in the cold, as stated earlier. This just didn't seam correct to me, so I called John at Cope Racing Trans. (were I got my trans.). He told me to go through the rad first to get it to the engine temp 1st, and then further bring the temp down by running it through the external cooler.