How to clear steering gear box out

[Fordman487]

I need advice on how to clean old grease out of a steering gear box-

Someone put Kendall SHP general grease in the steering box. It seems to work fine but I need to add some. I'm at a crossroads weather to add more generic grease or try to get all the old stuff out to add 90weight or JD Corn Head grease. Any thoughts? How am I going to get it all out without taking it apart?!?