I am changing the fluid completely to synthetic and I need to start the car and pump out the old fluid as I pour new fluid in. My question is which hose on the radiator is the return hose and which hose is the supply hose?

Any thoughts on needing or suggesting an additional external cooler just to keep the temp down?

I got the fluid changed and decided not to pump the old fluid out of the converter. I just drained it and changed the filter and refilled it. It took a little over 7 qts. I will do it again in about 20,000 miles to get rid of more old fluid. I also reused the pan gasket and so far no leaks.

This is a good method, but it is still better preventative maintenance to have the system FLUSHED and filter changed. I always do drain, refill, drive, drain, filter, all in the same day.

I'd recommend doing the second drain in about 5-10k.

Otherwise have it flushed.