Power steering fluid best brand?

First time changing out fluid and I have no clue what brand of psf to use. Truck is an 04 silverado 1500. I've read amsoil, atf… does it really matter? Also should I run sythentic or regular? Idk what was in the truck before...

Also I removed the gear box from my truck and drained all the fluid in the system from the 2 lines that hook up to it. (Not sure if that was the right way to do it but.. :think: ) anyways when I fill the reservoir back with fluid how do I bleed the system? Wheels in the air and rotate the steering wheel lock to lock multiple times I'm assuming? Just wanna make sure I do it this right
Thanks in advance