Can I add engine coolant while slowly draining to avoid bleeding?

The short answer is yes. Many people with the Gen 2 do coolant like that, including me on my personal cars.
Drain a gallon, add a gallon. (or whatever you prefer) Drive on like donkey kong.....do a gallon every year or two and it will keep the coolant chemicals just fine.

 

Probably.
Do it cold.
Add new at the highest point or as near as possible and drain at the lowest point.
This is assuming that the pressure cap is on the actual radiator and not on an "overflow" bottle.

If you are reasonably sure that it has been changed once before in it's life, I wouldn't even bother.........unless the present coolant looks "nasty".

 

Thanks! How do you do it, drain a little bit, close the drain valve, then add a little through the radiator cap?

Exactly. There's a drain at the bottom of the radiator. If you wanted to get real fancy, you could probably clamp the radiator hoses, completely drain the radiator, refill it and then take off the clamps. No loss of coolant from any other portion of the system. This assumes there's no spring on the inside of the suction hose though. I may have to check that out!

 

I bought a coolant refill tool years ago and no air bleeding is needed. I have done the procedure in the Prius and several cars.
https://a.co/d/gusKu1h