Not sure on yours with a steering box but on rodeos with R&P steering you just let it idle while rotating the wheels back and forth. Do it several times and eventually all the fluid has been run through at least once. Dont go all the way to the bumpstop, just close to it. When you hit the bump stop the system over pressurizes and opens the bypass valve in the pump so its not pushing any through the system at that point.

Billy, you might want to let a shop do the lower bushings. I know Steve fought with his for quite a while before putting it all back together and taking it to a shop. The shop I took mine to hammered, torched, and pressed for 8 hrs to do mine and I was told to NEVER bring another damn isuzu to them for lower bushings. The rear lower ones are pressed into the frame and are a biatch to do.